Chapter 27: Scombrotoxin (Histamine) Formation

Updated 9/21/00

Potential Food Safety Hazard

Scombrotoxin formation

Control Measures

Detection

FDA Guidelines
Analytical Procedures
Scombroid Poisoning Mechanism
Commercial Test Products
References

Potential Food Safety Hazard

Scombrotoxin formation as a result of time/temperature abuse of certain species of fish can cause consumer illness. The illness is most closely linked to the development of histamine in these fish. In most cases histamine levels in illness-causing fish have been above 200 ppm, often above 500 ppm (FDA, 1998a).

There are indications that decomposition can result in the production of other toxins (e.g., biogenic amines, such as putrescine and cadaverine) that have the potential to cause illness, even in the absence of histamine formation. Such illnesses have been reported in a number of fish species (FDA, 1998b).

Scombroid poisonings have primarily been associated with the consumption of tuna, mahi mahi, and bluefish. However, Table 27-1 lists a number of species that are also capable of developing elevated levels of histamine when temperature abused (FDA, 1998a).

Table 27-1. Vertebrate species capable of developing histamine.

Market Names Latin Names

Amberjack or Yellowtail Seriola spp.

Anchovy Anchoa spp.

Anchoviella spp.

Cetengraulis mysticetus

Engraulis spp.

Stolephorus spp.

Bluefish Pomatomus saltatrix

Bonito Cybiosarda elegans

Gymnosarda unicolor

Orcynopsis unicolor

Sarda spp.

Escolar or Snake Mackerel Lepidocybium flavobrunneum

Ruvettus pretiosus

Gemfish Lepidocybium flavobrunneum

Herring Etrumeus teres

Harengula thrissina

Ilisha spp.

Opisthopterus tardoore

Pellona ditchela

Herring or Sea or Sild and roe Clupea spp.

Herring,Thread Opisthonema spp.

Jack Caranx spp.

Oligoplites saurus

Selene spp.

Seriola rivoliana

Urapsis secunda

Jack or Blue Runner Caranx crysos

Jack or Crevalle Alectis indica

Jack or Rainbow Runner Elagatis bipinnulata

Jack or Roosterfish Nematistius pectoralis

Jobfish Aphareus spp.

Aprion virescens

Pristipomoides spp.

Kahawai Arripis spp.

Mackerel Gasterochisma melampus

Grammatorcynus spp.

Rastrelliger kanagurta

Scomber scombrus

Mackerel, Chub Scomber spp.

Mackerel, Jack Trachurus spp.

Mackerel, Spanish Scomberomorus spp.

Scomberomorus cavalla

Mahi-Mahi, Aquacultured or Wild Coryphaena spp.

Marlin Makaira spp.

Tetrapturus spp.

Pilchard or Sardine Sardina pilchardus

Sardinops spp.

Sardine Harengula spp.

Sardinella spp.

Saury Cololabis saira

Scomberesox saurus

Shad and roe Alosa spp.

Shad, Gizzard Dorosoma spp.

Nematalosa vlaminghi

Snapper Pristipomoides spp.

Sprat or Bristling Sprattus spp.

Trevally Caranx sexfasciatus

Tuna (small) Allothunnus fallai

Auxis spp.

Euthynnus spp.

Katsuwonus pelamis

Thunnus tonggol

Tuna (large) Thunnus alalunga

Thunnus albacares

Thunnus atlanticus

Thunnus maccoyii

Thunnus obesus

Thunnus thynnus

Wahoo Acanthocybium solandri

Yellowtail or Amberjack Seriola lalandei

Contents

Scombrotoxin formation

Certain bacteria produce the enzyme histidine decarboxylase during growth. This enzyme reacts with free histidine, a naturally occurring chemical that is present in larger quantities in some fish than in others. The result is the formation of histamine.

Histamine-forming bacteria are capable of growing and producing histamine over a wide temperature range. Growth is more rapid, however, at high-abuse temperatures (e.g., 21.1ºC (70ºF]) than at moderate-abuse temperatures (e.g., 7.2ºC [45ºF]). Growth is particularly rapid at temperatures near 32.2ºC [90ºF]). Histamine is more commonly the result of high temperature spoilage than of long term, relatively low temperature spoilage. Nonetheless, there are a number of opportunities for histamine to form under more moderate conditions.

Once the enzyme histidine decarboxylase has been formed, it can continue to produce histamine in the fish even if the bacteria are not active. The enzyme can be active at or near refrigeration temperatures. The enzyme is likely to be more stable than the bacteria in the frozen state and may be reactivated very rapidly after thawing. Recent studies suggest that if histamine production is advanced (i.e., high levels of histidine decarboxylase), histamine formation can continue even in frozen storage.

Freezing for an extended period of time (e.g., 24 weeks) may inactivate the enzyme-forming bacteria. Cooking can inactivate both the enzyme and the bacteria. However, once the toxin is formed, it cannot be eliminated by heat (including retorting) or freezing. After cooking, recontamination of the fish with the enzyme-forming bacteria is necessary for additional histamine to form. For these reasons, histamine development is more likely in raw, unfrozen fish.

The kinds of bacteria that are associated with histamine development are commonly present in the salt-water environment. They naturally exist on the gills and in the gut of live fish, with no harm to the fish. Upon death, the defense mechanisms of the fish no longer inhibit bacterial growth, and histamine-forming bacteria start to grow and produce histamine. With some harvesting practices, such as longlining, death can occur before the fish is removed from the water. Under the worst conditions histamine formation can already be underway before the fish is landed on the vessel. This condition can be aggravated when the fish is allowed to struggle on the line for a period of time, a situation that in certain tuna species may cause its internal temperature to increase to a more favorable growth range for the enzyme-forming bacteria.

The potential for histamine formation is increased when the flesh of the fish is directly exposed to the enzyme-forming bacteria. This occurs when the fish are processed (e.g., butchering or filleting) (FDA, 1998a).

Contents

Control Measures

Rapid chilling of fish immediately after death is the most important element in any strategy for preventing the formation of scombrotoxin. For fish other than tuna above 20 lbs. (9.1 kg), if the fish have not been exposed to temperatures above 28.3ºC (83ºF), the fish should be placed in refrigerated seawater or brine at 10ºC (50ºF) or less within 9 hours of death, or placed in ice within 12 hours of death. For tuna above 20 lbs. (9.1 kg), or if the fish have been exposed to temperatures above 28.3ºC (83ºF), the internal temperature of the fish should be brought to 10ºC (50ºF) or less within 6 hours of death. This will prevent the rapid formation of the enzyme histidine decarboxylase. Once this enzyme is formed control of the hazard is unlikely.

Further chilling towards the freezing point is also desirable to safeguard against longer-term, low-temperature development of histamine. Additionally, the shelf life of the fish is significantly compromised when product temperature is not rapidly dropped to near freezing.

The time required to lower the internal temperature of fish after capture will be dependent upon a number of factors, including:

The harvest method;
Delays in removing fish from a long line may significantly limit the amount of time left for chilling and may allow the fish to heat up as it struggles;

The quantity of fish landed in a purse seine may exceed a vessel's ability to rapidly chill the product;

The size of the fish;
The chilling method;

Ice alone takes longer to chill than does an ice slurry or recirculated refrigerated sea water or brine, a consequence of reduced contact area;
The quantity of ice or ice slurry and the capacity of refrigerated sea water or brine systems must be suitable for the quantity of catch.

Once chilled, the fish should be maintained as close as possible to the freezing point (or held frozen) until it is consumed. Exposure to ambient temperature should be minimized. The allowable exposure time is dependent primarily upon the speed with which the fish were chilled on-board the harvest vessel and whether the fish has been previously frozen (e.g., on-board the harvest vessel).

Unfrozen scombrotoxin-forming fish has a safe shelf life that is dependent upon the storage temperature. Table 27-2 shows an approximate safe shelf life for fish stored at various temperatures. The safe shelf-life periods in the table include the time aboard the harvest vessel (FDA, 1998a).

Table 27-2. Approximate Safe Shelf life for Fish at Various Storage Temperatures.

Product Temperature Safe Shelf-life (d)
with Rapid Cooling Safe Shelf-life (d)
with Delayed Cooling

-17.8ºC (0ºF) No limit No limit

0ºC (32ºF) 14 8

3.3ºC (38ºF) 10 7

4.4ºC (40ºF) 7 5

10ºC (50ºF) 3 0

21.1ºC (70ºF) 0 0

32.2ºC (90ºF) 0 0

Any time above 4.4ºC (40ºF) significantly reduces the expected safe shelf life. For this reason, fish should not be exposed to temperatures above 4.4ºC (40ºF) for more than four hours, cumulatively, after chilling on board the harvest vessel. The safety of this limit is dependent upon proper handling at sea.

Fish that have been handled particularly well on-board the harvest vessel may be able to safely withstand somewhat more exposure to elevated temperatures during post-harvest handling.

Fish that have undergone extended frozen storage (e.g., 24 weeks) can safely withstand considerably more exposure to elevated temperatures during post-harvest handling. Such fish should not be exposed to temperatures above 4.4ºC (40ºF) for more than twelve hours, cumulatively, after chilling on board the harvest vessel. An uninterrupted period of exposure should not exceed six hours. Intermittent refrigeration breaks the cycle of rapid bacterial growth and slows the formation of histamine. The safety of these limits is again dependent upon proper handling at sea.

Extended frozen storage (e.g., 24 weeks) or cooking minimizes the risk of additional histamine development by inactivating the enzyme-forming bacteria and, in the case of cooking, the enzyme itself. As previously mentioned, recontamination with enzyme-forming bacteria and significant temperature abuse is necessary for histamine formation under these conditions. Such recontamination may not be likely if the fish is processed under a conscientious sanitation program (FDA, 1998a).

Contents

Detection

Sensory evaluation is generally used to screen fish for spoilage odors that develop when the fish is exposed to time/temperature abuse. It is an effective means of detecting fish that have been subjected to a variety of abusive conditions.

However, odors of decomposition that are typical of relatively low temperature spoilage may not be easily detected if the fish has undergone high temperature spoilage. This condition makes sensory examination alone an ineffective control for scombrotoxin.

Chemical testing is an effective means of detecting the presence of histamine in fish flesh. However, the validity of such testing is dependent upon the design of the sampling plan. For this reason, chemical testing alone will not normally provide adequate assurance that the hazard has been controlled. Because histamine is generally not uniformly distributed in a decomposed fish, a guidance level of 50 ppm has been set. If 50 ppm is found in one section, there is the possibility that other sections may exceed 500 ppm. Additionally, recent studies suggest that if histamine production is advanced, histamine formation can continue even in frozen storage.

Observations of loins of tuna after the precooking step for the presence of "honeycombing" is also a valuable means of screening for fish that have been exposed to the kinds of temperature abuse that can lead to histamine development. Any fish that demonstrate the trait should be destroyed.

Control measures for "scombrotoxin formation" can include:

Making sure through harvest vessel records that incoming fish were properly handled on-board the harvest vessel, including:

Rapidly chilling the fish immediately after death;
Controlling on-board refrigeration (other than frozen storage) temperatures;
Proper on-board icing;

Testing incoming fish for histamine levels;
Making sure that incoming fish were handled properly during refrigerated transportation from the previous processor, including:

Controlling refrigeration temperatures during transit;
Proper icing during transit;

Checking incoming fish to ensure that they are not at an elevated temperature at time of receipt;
Checking incoming fish to ensure that they are properly iced or refrigerated at time of receipt;
Performing sensory examination on incoming fish to ensure that they do not show signs of decomposition;
Controlling refrigeration temperatures in your plant;
Proper icing in your plant;
Controlling the amount of time that the product is exposed to temperatures that would permit histamine formation during processing (FDA, 1998a).

Contents

FDA Guidelines

Table 27-3. FDA guidelines for tuna, mahi mahi, and related fish.

Guideline Reference

500 ppm set based on toxicity. 50 ppm set as defect action level, because histamine is generally not uniformly distributed in a decomposed fish. Therefore, if 50 ppm is found in one section, there is the possibility that other units may exceed 500 ppm. FDA, 1998c

Contents

Analytical Procedures

Histamine by capillary electrophoresis (Mopper and Sciacchitano, 1993)
Histamine in canned fish: High performance liquid chromatography method (Yen and Hsieh, 1991).
Histamine in canned tuna: Fluorometric method (Lerke and Bell, 1976).
Histamine in fish products: Thin layer chromatographic method (Schutz et al., 1976).
Histamine in fish: Enzyme-based screening test (Lerke et al., 1983).
Histamine in fish: Fluorometric method (Taylor et al., 1978).
Histamine in fish: Oxygen-sensor-based method (Ohashi et al., 1994).
Histamine in seafood: Biological method (AOAC, 1995a).
Histamine in seafood: Chemical method (AOAC, 1995b).
Histamine in seafood: Flow-injection method (Hungerford et al., 1990).
Histamine in seafood: Fluorometric method (AOAC, 1995c).
Histamine in tuna: Copper chelation method (Bateman et al., 1994).
Histamine in unprocessed and canned fish: Guinea pig ileum method (Geiger, 1944).

Contents

Scombroid Poisoning Mechanism

Inhibitors of histaminase enzymes (Hungerford and Arefyev, 1992)

Contents

Commercial Test Products

Table 27-4. Commercial test products for histamine.

Test

Analytical Technique
Approx.
Total Test Time

Supplier

ALERT^® for Histamine
[Sensitivity: 5-50 ppm, qualitative] ELISA
2 h
Neogen Corporation
620 Lesher Pl.
Lansing, MI 48912
Phone: 800/234-5333; 517/372-9200
E-mail: neogen-info@neogen.com
Web: www.neogen.com

Histamarine Test Kit¹
[Sensitivity: 0.5 ppm, quantitative from 1 to 500 ppm] Enzyme immunoassay
1 h
Immunotech
Contact: Alain Artus
130, av. Delattre de Tassigny
B.P. 177
13276 Marseille Cedex 9
FRANCE
Phone: 33 491 17 27 46
E-mail: artus@immunotech.fr
Web: www.immunotech.fr

EIA for Histamine in Fish Extract, K1-HTM [Sensitivity: 2.5 ppm, quantitative 1-50 ppm] Enzyme immunoassay
90 min
Immuno-Diagnostic Reagents
Contact: Siong Wie
P.O. Box 2659
Vista, CA 92085-2659
Phone: 858/350-9608
E-mail: idr@tiora.net
Web: www.tiora.net/~idr/

EIA for Histamine Fishmeal and Bonemeal, K2-HTM
[Sensitivity: 5 ppm, qualitative] Enzyme immunoassay
35 min
Immuno-Diagnostic Reagents
Contact: Siong Wie
P.O. Box 2659
Vista, CA 92085-2659
Phone: 858/350-9608
E-mail: idr@tiora.net
Web: www.tiora.net/~idr/

EIA for Histamine in Raw and Canned fish, K3-HTM
[Sensitivity: 5 ppm, qualitative] Enzyme immunoassay
35 min
Immuno-Diagnostic Reagents
Contact: Siong Wie
P.O. Box 2659
Vista, CA 92085-2659
Phone: 858/350-9608
E-mail: idr@tiora.net
Web: www.tiora.net/~idr/

RIDASCREEN^® Histamin R1602
[Sensitivity: 2.5 ppm; quantitative] ELISA
2 h
R-Biopharm, Inc.
Contact: Thomas Grace
7950 US 27 South
Marshall, MN 49068
Phone: 616/789-3033
E-mail: RbioST@voyager.net

Transia Plate Histamine
[Semi-quantitative assay; from 25 to 200 ppm] ELISA
1 h
Diffchamb AB
Baika Barg` gata 7
42246 Hisings Baika Sweden
Phone: 46-31-58-3270
E-mail: market.dept@diffchamb.se Web: www.diffchamb.com

Transia Plate Histamine
[Qualitative assay; threshold at 100 ppm] ELISA
1 h
Diffchamb AB
Baika Bargögata 7
42246 Hisings Baika Sweden
Phone: 46-31-58-3270
E-mail: market.dept@diffchamb.se Web: www.diffchamb.com

Veratox^®for Histamine
[Sensitivity: < 5ppm, quantitative from 0 to 50 ppm] ELISA
1 h
Neogen Corporation
620 Lesher Pl.
Lansing, MI 48912
Phone: 800/234-5333; 517/372-9200
E-mail: neogen-info@neogen.com
Web: www.neogen.com

¹AOAC Approved

Contents

References

AOAC. 1995a. Histamine in seafood: Biological method. Sec. 35.1.30, Method 954.04. In Official Methods of Analysis of AOAC International, 16th ed., P.A. Cunniff (Ed.), p.14-15. AOAC International, Gaithersburg, MD.

AOAC. 1995b. Histamine in seafood: Chemical method. Sec. 35.5.31, Method 957.07. In Official Methods of Analysis of AOAC International, 16th ed., P.A. Cunniff (Ed.), p.15-16. AOAC International, Gaithersburg, MD.

AOAC. 1995c. Histamine in seafood: Fluorometric method. Sec. 35.1.32, Method 977.13. In Official Methods of Analysis of AOAC International, 16th ed., P.A. Cunniff (Ed.), p. 6-17. AOAC International, Gaithersburg, MD.

Bateman, R.C., Eldrige, D.B., Wade, S., McCoy, Messer, J., Jester, E.L.E., and Mowdy, D.E. 1994. Copper chelation assay for histamine in tuna. J. Food Sci. 59(3):517-518, 543.

FDA. 1998a. Scombrotoxin (histamine) formation. Ch. 7. In Fish and Fishery Products Hazards and Controls Guide. 2^nd ed., p. 73-90. Department of Health and Human Services, Public Health Service, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.

FDA. 1998b. Other Decomposition-Related Hazards. Ch. 8. In Fish and Fishery Products Hazards and Controls Guide. 2^nd ed., p. 91-92. Department of Health and Human Services, Public Health Service, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.

FDA. 1998c. FDA & EPA Guidance Levels. Appendix 5. In Fish and Fishery Products Hazards and Controls Guide. 2^nd ed., p. 245-248. Department of Health and Human Services, Public Health Service, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.

Geiger, E. 1944. Histamine content of unprocessed and canned fish. A tentative method for quantitative determination of spoilage. Food Research 9(4):293-297.

Hungerford, J.M. and Arefyev, A.A. 1992. Flow-injection assay of enzyme inhibition using immobilized diamine oxidase. Anal. Chem. Acta 26:351-359.

Hungerford, J.M., Walker, K.D., Wekell, M.M., LaRose, J.E., and Throm, H.R. 1990. Selective determination of histamine by flow injection analysis. Anal. Chem.62(0):1971-1976.

Lerke, P.A., Porcuna, M.N., and Chin, H.B. 1983. Screening test for histamine in fish. J. Food Sci. 48:155-157.

Lerke, P.A. and Bell, L.D. 1976. A rapid fluorometric method for the determination of histamine in canned tuna. J. Food Sci. 41:1282-1284.

Mopper, B. and Sciacchitano, C.J. 1993. Capllary zone electrophoretic determination of histamine in fish. JAOAC 77(4):881-883.

Ohashi, M., Nomura, F., Suzuki, M., Otsuka, M., Adachi, O., and Arakawa, N. 1994. Oxygen-sensor-based simple assay of histamine in fish using purified amine oxidase. J. Food Sci. 59(3):519-522.

Schutz, D.E., Chang, G.W., and Bjeldanes, L.F. 1976. Rapid thin layer chromatographic method for the determination of histamine in fish products. J. AOAC. 59(6):1224-1225.

Taylor, S.L., Lieber, E.R., and Leatherwood, M. 1978. A simplified method for histamine analysis of foods. J. Food Sci. 43:247-250.

Yen G. and Hsieh, C. 1991. Simultaneous analysis of biogenic amines in canned fish by HPLC. J. Food Sci. 56(1):158-160.

Market Names	Latin Names
Amberjack or Yellowtail	Seriola spp.
Anchovy	Anchoa spp.
	Anchoviella spp.
	Cetengraulis mysticetus
	Engraulis spp.
	Stolephorus spp.
Bluefish	Pomatomus saltatrix
Bonito	Cybiosarda elegans
	Gymnosarda unicolor
	Orcynopsis unicolor
	Sarda spp.
Escolar or Snake Mackerel	Lepidocybium flavobrunneum
Escolar or Snake Mackerel	Ruvettus pretiosus
Gemfish	Lepidocybium flavobrunneum
Herring	Etrumeus teres
	Harengula thrissina
	Ilisha spp.
	Opisthopterus tardoore
	Pellona ditchela
Herring or Sea or Sild and roe	Clupea spp.
Herring,Thread	Opisthonema spp.
Jack	Caranx spp.
	Oligoplites saurus
	Selene spp.
	Seriola rivoliana
	Urapsis secunda
Jack or Blue Runner	Caranx crysos
Jack or Crevalle	Alectis indica
Jack or Rainbow Runner	Elagatis bipinnulata
Jack or Roosterfish	Nematistius pectoralis
Jobfish	Aphareus spp.
	Aprion virescens
	Pristipomoides spp.
Kahawai	Arripis spp.
Mackerel	Gasterochisma melampus
	Grammatorcynus spp.
	Rastrelliger kanagurta
	Scomber scombrus
Mackerel, Chub	Scomber spp.
Mackerel, Jack	Trachurus spp.
Mackerel, Spanish	Scomberomorus spp.
Mackerel, Spanish	Scomberomorus cavalla
Mahi-Mahi, Aquacultured or Wild	Coryphaena spp.
Marlin	Makaira spp.
Marlin	Tetrapturus spp.
Pilchard or Sardine	Sardina pilchardus
Pilchard or Sardine	Sardinops spp.
Sardine	Harengula spp.
Sardine	Sardinella spp.
Saury	Cololabis saira
Saury	Scomberesox saurus
Shad and roe	Alosa spp.
Shad, Gizzard	Dorosoma spp.
Shad, Gizzard	Nematalosa vlaminghi
Snapper	Pristipomoides spp.
Sprat or Bristling	Sprattus spp.
Trevally	Caranx sexfasciatus
Tuna (small)	Allothunnus fallai
	Auxis spp.
	Euthynnus spp.
	Katsuwonus pelamis
	Thunnus tonggol
Tuna (large)	Thunnus alalunga
	Thunnus albacares
	Thunnus atlanticus
	Thunnus maccoyii
	Thunnus obesus
	Thunnus thynnus
Wahoo	Acanthocybium solandri
Yellowtail or Amberjack	Seriola lalandei

Product Temperature	Safe Shelf-life (d) with Rapid Cooling	Safe Shelf-life (d) with Delayed Cooling
-17.8ºC (0ºF)	No limit	No limit
0ºC (32ºF)	14	8
3.3ºC (38ºF)	10	7
4.4ºC (40ºF)	7	5
10ºC (50ºF)	3	0
21.1ºC (70ºF)	0	0
32.2ºC (90ºF)	0	0

Guideline	Reference
500 ppm set based on toxicity. 50 ppm set as defect action level, because histamine is generally not uniformly distributed in a decomposed fish. Therefore, if 50 ppm is found in one section, there is the possibility that other units may exceed 500 ppm.	FDA, 1998c

Test	Analytical Technique	Approx. Total Test Time	Supplier
ALERT^® for Histamine [Sensitivity: 5-50 ppm, qualitative]	ELISA	2 h	Neogen Corporation 620 Lesher Pl. Lansing, MI 48912 Phone: 800/234-5333; 517/372-9200 E-mail: neogen-info@neogen.com Web: www.neogen.com
Histamarine Test Kit¹ [Sensitivity: 0.5 ppm, quantitative from 1 to 500 ppm]	Enzyme immunoassay	1 h	Immunotech Contact: Alain Artus 130, av. Delattre de Tassigny B.P. 177 13276 Marseille Cedex 9 FRANCE Phone: 33 491 17 27 46 E-mail: artus@immunotech.fr Web: www.immunotech.fr
EIA for Histamine in Fish Extract, K1-HTM [Sensitivity: 2.5 ppm, quantitative 1-50 ppm]	Enzyme immunoassay	90 min	Immuno-Diagnostic Reagents Contact: Siong Wie P.O. Box 2659 Vista, CA 92085-2659 Phone: 858/350-9608 E-mail: idr@tiora.net Web: www.tiora.net/~idr/
EIA for Histamine Fishmeal and Bonemeal, K2-HTM [Sensitivity: 5 ppm, qualitative]	Enzyme immunoassay	35 min	Immuno-Diagnostic Reagents Contact: Siong Wie P.O. Box 2659 Vista, CA 92085-2659 Phone: 858/350-9608 E-mail: idr@tiora.net Web: www.tiora.net/~idr/
EIA for Histamine in Raw and Canned fish, K3-HTM [Sensitivity: 5 ppm, qualitative]	Enzyme immunoassay	35 min	Immuno-Diagnostic Reagents Contact: Siong Wie P.O. Box 2659 Vista, CA 92085-2659 Phone: 858/350-9608 E-mail: idr@tiora.net Web: www.tiora.net/~idr/
RIDASCREEN^® Histamin R1602 [Sensitivity: 2.5 ppm; quantitative]	ELISA	2 h	R-Biopharm, Inc. Contact: Thomas Grace 7950 US 27 South Marshall, MN 49068 Phone: 616/789-3033 E-mail: RbioST@voyager.net
Transia Plate Histamine [Semi-quantitative assay; from 25 to 200 ppm]	ELISA	1 h	Diffchamb AB Baika Barg` gata 7 42246 Hisings Baika Sweden Phone: 46-31-58-3270 E-mail: market.dept@diffchamb.se Web: www.diffchamb.com
Transia Plate Histamine [Qualitative assay; threshold at 100 ppm]	ELISA	1 h	Diffchamb AB Baika Bargögata 7 42246 Hisings Baika Sweden Phone: 46-31-58-3270 E-mail: market.dept@diffchamb.se Web: www.diffchamb.com
Veratox^®for Histamine [Sensitivity: < 5ppm, quantitative from 0 to 50 ppm]	ELISA	1 h	Neogen Corporation 620 Lesher Pl. Lansing, MI 48912 Phone: 800/234-5333; 517/372-9200 E-mail: neogen-info@neogen.com Web: www.neogen.com