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AntihistaminesAntihistamines are antiallergic agents that neutralize the effects of the endogenous substance histamine. They are used, among other things, for hay fever, nettle rash, allergic conjunctivitis, skin diseases, sleep disorders, nausea, vomiting and colds. As sleeping pills and sedatives, and in children, they should be administered cautiously due to possible adverse effects. Older antihistamines in particular can trigger fatigue as an undesirable effect.

synonymous: H1 antagonists, H1 antihistamines, antihistamines


Antihistamines are often taken in the form of tablets. Drops, solutions, lozenges, capsules, gels, creams, eye drops, nasal sprays and injection solutions are also available.

As the first active ingredient from this group, phenbenzamine (Antergan®) was developed in France in the 1940s. It is no longer on sale today.

Structure and properties

The traditional antihistamines are alkylamines, ethylenediamines, phenothiazines, and piperazines. Today there are also representatives in the trade who do not belong to these groups. Antihistamines have played an important role as precursors to the neuroleptics and the antidepressants.


Antihistamines (ATC R06) have antihistamines, antiallergic, antipruritic and anti-inflammatory properties. Some of them are also:

Antihistamines are inverse agonists on the histamine H1 receptor, i.e. they stabilize the receptor in its inactive conformation. Thereby they cancel the effects of histamine and alleviate allergic complaints. So antihistamines are not histamine receptor antagonists.

Mechanism of action of antihistamines, click to enlarge. Illustration © PharmaWiki


The areas of application include:

1st generation active ingredients

First-generation active ingredients are generally not specific for the H1 receptor, are anticholinergic, cross the blood-brain barrier and reach the brain. There they trigger central disorders such as tiredness, sleepiness and dizziness because they interact with central receptors. They have a shorter duration of action than 2nd generation antihistamines and must therefore be administered more frequently. 1st generation antihistamines are controversial and should be used cautiously and for some areas of application no longer at all:

No longer available in Switzerland:

2nd generation active ingredients

Second generation drugs are generally specific for the H1 receptor and less depressant. They are therefore also referred to as “non-sedating antihistamines”, but less often they can also cause tiredness. They do not cross the blood-brain barrier, are specific for the H1 receptor and are not anticholinergic. They also have a longer duration of action of 12 to 24 hours and therefore only need to be administered once a day.

The following active ingredients are not or no longer on the market in Switzerland:

External antihistamines

Eye drop:

Nasal sprays:


see also

Antihistamine eye drops, antihistamine nasal sprays, H2 antihistamines, hay fever, allergic conjunctivitis, urticaria

  • Medicinal product information (CH)
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  • Wiest E., Jones J.S. Towards evidence-based emergency medicine: best BETs from the Manchester Royal Infirmary. BET 1: Use of non-sedating antihistamines in the common cold. Emerg Med J, 2011, 28 (7), 632-3 Pubmed

Conflicts of Interest: None / Independent. The author has no relationships with the manufacturers and is not involved in the sale of the products mentioned.

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