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Allergies > Antihistamines

Antihistamines

Antihistamines are very good at treating the following symptoms of allergic rhinitis:

- sneezing
- an itchy nose
- a runny nose

They are less effective at treating a blocked nose.

What Antihistamines are Currently Available

There are two main types of antihistamines:

- first-generation antihistamines
- second-generation antihistamines

Second-generation antihistamines are generally recommended for treating allergic rhinitis, because, unlike first-generation antihistamines, they do not cause tiredness.

For your reference, we have provided a list of currently available first-generation and second-generation antihistamines. Your doctor can advise you on which should be best for you.

Read our article about the basics of allergy testing

First-Generation Antihistamines

The following table gives some examples of first-generation antihistamines available in the UK, US, and Canada for the treatment of allergic rhinitis. Only brand name drugs are listed, but generic versions may also be available.

Second-Generatiion Antihistamines

The following table gives some examples of second-generation antihistamines available in the UK, US, and Canada for the treatment of allergic rhinitis. Only brand name drugs are listed, but generic versions may also be available.

How do i get Antihistamines

Most first and second-generation antihistamines can be bought from your local pharmacy, but some require a prescription from your doctor. You should visit your doctor to see which treatment would be best for your symptoms.

How do i take Antihistamines

Most antihistamines are taken as tablets. Syrups are also available for use by children, eg cetirizine for children 2 years and older, and loratadine for children 6 years and older.

First-generation antihistamines may need to be taken 3–4 times a day. Second-generation antihistamines have longer effects, and may need to be taken only once a day.

Some second-generation antihistamines, eg azelastine and levocabastine, are also available as nasal sprays, and as eye-drops for treating allergic rhinoconjunctivitis. These treat symptoms quicker than antihistamines taken orally and are effective at low doses. They may also help to treat a blocked nose. They will only treat the area to which they are applied, and must be taken twice daily. They do not cause sedation, but they may have a bitter taste.

How Effective and Safe are First-Generation Antihistamines?

These were the first antihistamines to be developed. They are effective at treating allergic rhinitis, but may cause tiredness.

The sedative effects of first-generation antihistamines have been linked to car and work-related accidents. People who take them may not be aware of being drowsy, and this increases the risk. In children, tiredness may reduce learning ability and academic performance. Drowsiness may last for many hours, and even when taken in the evening, sedation may occur the next day. In combination with certain other drugs, eg alcohol, sedatives, and anti-depressants, the sedative effects may be worsened.

Other side effects include not being able to pass urine, blurred vision, dilated pupils, and a dry mouth.

How Effective and Safe are Second-Generation Antihistamines?

These are effective at treating allergic rhinitis, and are less likely to cause tiredness than first-generation antihistamines. People whose occupations require concentration should certainly use these. Some industries only allow the use of second-generation antihistamines eg transport sectors. Children should be given non-sedating antihistamines as tiredness reduces the ability to learn.

Although sedation is minimal from second-generation antihistamines, you should still take care as people react differently to drugs. Elderly people may be at greater risk from sedation.

What Drugs can i take at the same time?

In some cases, a combination of different drugs may be useful in treating allergic rhinitis. Your doctor can advise you on whether you may benefit from this.

Antihistamines and decongestants

Antihistamines are good at treating sneezing, an itchy nose, and a runny nose, but they are less good at treating a blocked nose. They may therefore be used at the same time as oral decongestants, which are effective at relieving a blocked nose.

Combinations of antihistamines and decongestants can counteract all the symptoms of allergic rhinitis on a short-term basis.

Topical corticosteroids and antihistamines

Topical corticosteroids and antihistamines are both very good at treating a runny nose, sneezing, and an itchy nose, and topical corticosteroids are also good at treating a blocked nose. If you have severe allergic rhinitis, your doctor may advise that you use both topical corticosteroids and antihistamines to control your symptoms.

References

Day J. Pros and cons of the use of antihistamines in managing allergic rhinitis. J Allergy Clin Immunol 1999;103:S395–S399.

Dykewicz MS, Fineman S, Skoner DP, et al. Diagnosis and management of rhinitis: complete guidelines of the Joint Task Force on Practice Parameters in Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol 1998;81:478–518.

Kay CG. The effects of antihistamines on cognition and performance. J Allergy Clin Immunol 2000;105:S622–S627.

van Cauwenberge P, Bachert C, Passalacqua G, et al. Consensus statement on the treatment of allergic rhinitis. European Academy of Allergology and Clinical Immunology. Allergy 2000;55:116–134.