Allergy Medicines Explained (Antihistamines): Which One and When

Reviewed by Dr Asma

Sneezing fits, a runny nose, itchy eyes, a rash that appears from nowhere. Allergy is one of the most common reasons people walk into a pharmacy in Pakistan, especially when the seasons change or smog settles over the city. The shelves are full of allergy medicines with unfamiliar names, and many people take whatever worked for a friend. This guide explains how the main groups of allergy medicines work, what side effects to expect, and which questions to take to your doctor.

What actually happens in an allergy?

When your body meets a trigger such as dust, pollen, pet hair or a food, it releases a chemical called histamine. Histamine causes the itching, sneezing, watery eyes, swelling and hives. Most allergy medicines either block histamine, calm the inflammation it causes, or reduce the swelling inside the nose. Knowing which symptom bothers you most helps you pick the right group.

The main groups of allergy medicines

Antihistamine tablets and syrups. These block histamine and are the first choice for sneezing, itching, hives and a runny nose. They come in two broad types. Older (first generation) antihistamines work well but often cause strong drowsiness and a dry mouth. Newer (second generation) ones such as cetirizine, levocetirizine, loratadine, fexofenadine and desloratadine usually cause much less sleepiness, although some people still feel a little tired.

Nasal sprays. Steroid nasal sprays are very effective for a constantly blocked or runny nose, but they work best when used regularly for several days rather than occasionally. Antihistamine sprays act faster. Decongestant sprays give quick relief, but using them for more than a few days can make the blockage worse, so keep them for short use only.

Allergy eye drops. For itchy, watery eyes, drops are usually better than tablets. Read more in our guide to eye care products.

Creams and lotions. Calamine, mild steroid creams and moisturisers can soothe skin allergy. Steroid creams should be used only as your doctor or pharmacist advises, and not on the face for long periods.

Steroid tablets or injections. These are kept for severe flare ups and are given by a doctor for a short course. They should never be used casually.

You can explore the range in our Allergy category. If your doctor has written a prescription, send it through the upload prescription page.

Side effects worth knowing about

• Drowsiness: common with older antihistamines. Avoid driving or operating machinery until you know how a medicine affects you.
• Dry mouth, dry eyes and difficulty passing urine: can happen with older types, and men with an enlarged prostate should be especially careful.
• Headache or stomach upset: possible with most tablets. Taking the medicine with food can help.
• Nosebleeds or dryness: can occur with nasal sprays. Aim the spray away from the centre of the nose.
• Combination cold and flu products: many already contain an antihistamine, so taking an extra allergy tablet on top can double up the effect.

Special situations

Children. Never give adult tablets. Child syrups exist, but the right product and amount depend on age and weight, so ask your doctor or pharmacist. Do not use sedating syrups just to make a child sleep.

Pregnancy and breastfeeding. Some antihistamines are considered safer than others, but this must be decided with your doctor.

Elderly people. Older antihistamines can cause confusion, dizziness and falls. Newer options are usually preferred.

Other medicines. Antihistamines can add to the drowsiness caused by sleeping tablets, anxiety medicines and some painkillers. Always tell the pharmacist what else you take.

Reduce the trigger, not just the symptoms

Medicine controls symptoms, but cutting down exposure makes a big difference. Wash bedding in hot water weekly, keep windows closed on smoggy or dusty days, use a damp cloth rather than a dry duster, and keep pets out of the bedroom if they are a trigger. Our article on dust allergy and allergic rhinitis has a detailed home routine, and the smog protection guide helps in winter.

Emergency warning signs

Swelling of the lips, tongue or face, difficulty breathing, wheezing, dizziness or fainting after a food, insect sting or medicine can be a severe allergic reaction called anaphylaxis. This is an emergency. Go to the nearest hospital immediately and do not wait for a tablet to work.

What to ask your doctor

• Do I need a tablet, a nasal spray, eye drops, or a combination?
• Is this medicine likely to make me sleepy, and when is the best time to take it?
• How long should I use it, and can I stop when I feel better?
• Should I get tested to find my trigger?
• Is this safe with my other medicines or my other health conditions?

Frequently asked questions

Can I take an antihistamine every day?

Some people with long term allergy do, but only after discussing it with a doctor. Daily use for months should be reviewed.

Why does my antihistamine make me sleepy?

Antihistamines can reach the brain and cause drowsiness, especially older types. A newer non sedating type may suit you better.

Are allergy tablets and cold tablets the same?

No. Cold products often combine several ingredients. Check the label so you do not take the same ingredient twice.

Do allergy medicines cure allergy?

No. They control symptoms. Avoiding triggers and, in selected cases, allergy specific treatment from a specialist address the cause.

Is it safe to keep using a nasal decongestant spray?

Not for long. More than a few days can cause rebound blockage. Ask your doctor about a steroid spray for long term problems.

Important note

This article is for general information only and does not replace medical advice. Please consult a doctor or pharmacist before taking any medicine, particularly for children, pregnant or breastfeeding women, and people with other medical conditions.

Disclaimer: This article is for general information only and is not a substitute for medical advice. Please consult a qualified doctor or pharmacist before starting or changing any treatment.