April 16, 2018
Do you have spring allergies? Blame me.
What molecule am I?
Image of Histamine 3D Image of Histamine

Histamine is an organic triamine that is a strong vasodilator found in blood and most bodily tissues. It is involved in inflammatory and immune responses. Histamine is stored primarily in mast cells and basophils; it is released in response to tissue damage caused by injury, infection, or allergens.

In 1938, French microbiologists Lévy-Brühl and Ungar showed that pneumococcus bacteria and Balantidium coli biosynthesize histamine from the amino acid histidine. It was later shown that this reaction is catalyzed by the enzyme histidine decarboxylase.

Histamine has many physiological functions, but this time of year we focus on its role in reactions to allergens such as pollen. Allergens bind to the antibody immunoglobulin E in the mucous membranes of the nasal cavity, releasing histamine, and leading to runny noses, watery eyes, sneezing, and nasal congestion. Fortunately, many antihistamines are available to combat these symptoms.

Histamine hazard information

GHS classification*: acute toxicity, oral, category 3 
H301—Toxic if swallowed
GHS classification: skin irritation, category 2 
H315—Causes skin irritation 
GHS classification: skin sensitization, category 1
H317—May cause an allergic skin reaction
GHS classification: eye irritation, category 2A
H319—Causes serious eye irritation
GHS classification: respiratory sensitisation, category 1

H334—May cause allergy or asthma symptoms or breathing difficulties if inhaled

GHS classification: specific target organ toxicity, single exposure, category3
H335—May cause respiratory irritation

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

Histamine fast facts

CAS Reg. No.51-45-6
Molar mass111.15 g/mol 
Empirical formulaC5H9N3
AppearanceWhite crystals or powder
Melting point83–84 ºC
Water solubility34 g/L
Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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