April 16, 2018
Do you have spring allergies? Blame me.
What molecule am I?

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 fast facts

CAS Reg. No. 51-45-6
Molar mass 111.15 g/mol 
Empirical formula C5H9N3
Appearance White crystals or powder
Melting point 83–84 ºC
Water solubility 34 g/L

Histamine hazard information

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

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

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

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

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