Antihistamines - Side-effects and cautions

Authored by Dr Mary Harding, 05 Jul 2017

Patient is a certified member of
The Information Standard

Reviewed by:
Dr Helen Huins, 05 Jul 2017

Most people who take antihistamines do not have any serious side-effects. If side-effects do occur, they are usually minor. The most common are:

  • Drowsiness.
  • Headache.
  • Dizziness.
  • Agitation.
  • Dry mouth.
  • Blurred vision.
  • Difficulty passing urine (urinary retention).
  • Stomach and gut upsets (gastrointestinal discomfort).

For a full list of all the side-effects and possible interactions associated with your medicine, consult the leaflet that comes with your medication.

If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at the following web address:

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • The person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication - and/or the leaflet that came with it - with you while you fill out the report.

Most people can take antihistamines safely. Antihistamines should not be used by people with a rare metabolic disorder called acute porphyria. In addition, they may not be suitable for people with liver or kidney problems. First-generation antihistamines may not be suitable for men with prostate enlargement (benign prostatic hyperplasia). They may also not be suitable for people with raised pressure in the eye (acute glaucoma) or who are at risk of glaucoma.

Women who are pregnant or breast-feeding are usually advised not to take antihistamines. This is because it is not known if they do any harm and studies cannot be done on women in this situation just in case. However, they are not known to cause harm. If certain conditions such as hay fever or morning sickness make you very unwell in pregnancy, the benefit of treatment may be more than the very small risk of any harm. Your doctor would talk this over with you and prescribe one of the antihistamines believed to be safe in pregnancy if you choose to take one. Similarly, in breast-feeding women, in some cases the benefits may be more than the risk. Antihistamines do come through in small quantities into breast milk, although they are not known to cause any harm.

A full list of people who should not take antihistamines is included with the information leaflet that comes in the medicine packet. If you are prescribed or buy an antihistamine, read this to be sure you are safe to take it.

Further reading and references

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