Can I take antihistamines with asthma?

Why this happens

Older, first-generation antihistamines (like chlorphenamine) have 'anticholinergic' effects. This means they can reduce the amount of mucus in the airways, making the remaining mucus thicker and harder to cough up. This can potentially irritate the lungs or make a cough feel more 'tight'. Modern, non-drowsy antihistamines (like cetirizine or loratadine) have very little of this effect.

What you should do

If you have asthma, it is usually best to choose a modern, non-drowsy antihistamine (such as cetirizine, loratadine, or fexofenadine) rather than older, sedating ones. Always keep your blue 'reliever' inhaler with you. If you notice your chest feeling tighter or your cough becoming drier and more difficult after starting an antihistamine, stop taking it and speak to your GP or pharmacist.

Important precautions

Drowsiness and impairment

These medicines can cause severe drowsiness and significantly impair your ability to drive or operate machinery. The effect is greatly increased if you drink alcohol.

Mental health changes

Montelukast can cause serious neuropsychiatric events, including agitation, sleep disturbances, depression, and suicidal thoughts. If you notice any change in mood or behaviour, stop the medicine and contact a doctor immediately.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol when taking antihistamines. Alcohol significantly increases the sedative effects of these medicines, making you much more drowsy, dizzy, and clumsy, which increases the risk of accidents.

Fruit Juices (Grapefruit, Orange, Apple)

Do not drink grapefruit, orange, or apple juice while taking fexofenadine. These juices can significantly reduce the amount of medicine your body absorbs, making the treatment less effective. It is best to take fexofenadine with water.

Char-grilled or Flame-broiled foods

Eating large amounts of char-grilled meat can speed up how quickly your body clears these medicines, potentially making your asthma treatment less effective.

More about Theophylline

More about Aminophylline

Caffeine (Coffee, Tea, Energy drinks, Cola)

You should avoid or strictly limit drinks containing caffeine. Caffeine is chemically similar to theophylline and aminophylline and can increase the risk of side effects such as heart palpitations, tremors, anxiety, and difficulty sleeping.

High-protein or High-carbohydrate meals

Significant changes to your diet (such as starting a very high-protein or very high-carbohydrate diet) can change how your body processes theophylline and aminophylline. Consult your doctor before making major dietary changes.

Using other medicines

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.