They have been taken by a large number of pregnant women and women of childbearing age without any proven increase in malformations or harm to the fetus.An exception is promethazine for which adverse events have been reported in animal studies (at very high doses).Allergic rhinitis may be seasonal (usually due to grass, tree or weed pollens) or perennial (due to triggers such as pet hair, house dust mite or mould).It is important to ask the patient if they also have respiratory symptoms as a worsening in allergic rhinitis can lead to increased asthma symptoms.They are particularly useful for nasal itchiness, sneezing and rhinorrhoea, but are less effective for nasal obstruction.Oral antihistamines also have the benefit of treating associated conjunctival symptoms.However, pregnant women must be warned about the other aspects of safety such as sedation and consider whether they should not drive while taking these drugs.
For paediatric suspensions, the choice may be determined by a preferred flavour.
Avoiding trigger factors is the first step in the management of allergic rhinitis but some triggers can be difficult to avoid.
Drugs can help and oral antihistamines are one of the mainstays of treatment.
They are useful for treating the itching that results from the release of histamine.
The early so-called ‘first generation’ antihistamines, such as promethazine, caused sedation.
There is now little role for sedating antihistamines in allergic conditions.