Loratadine: uses, side effects and cautions

Loratadine relieves the symptoms of allergy, and the NHS lists hay fever, conjunctivitis with red itchy eyes, eczema, hives, reactions to insect bites and stings and some food allergies. It comes as tablets and as a liquid you swallow.

It is classed as a non-drowsy antihistamine, meaning it is much less likely than older sedating types such as chlorphenamine to make you sleepy.

On meeting pollen, animal fur, house dust or an insect sting, the body releases histamine, which causes itchy watery eyes, a running or blocked nose, sneezing and rashes. Loratadine blocks histamine's effects, so these symptoms ease. The NHS says relief typically begins within 1 to 3 hours.

Other non-drowsy antihistamines, including cetirizine, desloratadine, fexofenadine and levocetirizine, seem to work as well. Loratadine, desloratadine and fexofenadine seem less likely to cause sleepiness than cetirizine. If one does not suit you, another may.

The NHS gives the usual adult dose as 10mg once a day, as a 10mg tablet or liquid labelled 5mg/5ml or 1mg/1ml. If you have liver problems the dose is usually lower and may be taken every other day. For children the dose depends on weight or age; those aged 6 to 12 can only take the tablets if they weigh more than 30kg, and liquid is used for younger or lighter children.

Swallow tablets with water, milk or juice. A tablet scored across the middle may be broken in half but should not be chewed. It can be taken with or without food. Use the syringe or spoon supplied for liquid. Some people need it for a day or two after an insect bite, others regularly through the pollen season. If you forget, take it when you remember unless the next dose is nearly due.

Doctors sometimes suggest up to four times the usual dose for severe itchy rash or deep skin swelling (angioedema), but this is not suitable for everyone and should only follow medical advice. A sedating antihistamine at night is sometimes added when itching disturbs sleep.

The commonest side effect is sleepiness, affecting more than 1 in 100 people. Trying a different non-drowsy antihistamine may help, and you should not drive, cycle or use tools until you feel fully alert. Children may get headaches or feel tired or nervous.

Swelling of the lips, mouth, throat or tongue can signal a serious allergic reaction and needs 999. Taking more than the recommended dose is unlikely to harm, but contact NHS 111 if you or your child get a headache, a fast heartbeat or sleepiness, if you are concerned, or if the child is under 5 even without symptoms. Suspected side effects can be reported through the Yellow Card scheme.

Most adults and children aged 2 and over can take loratadine. Tell your doctor or pharmacist if you have ever had an allergy to it or to other medicines, have severe liver failure, are allergic to food additives, or have epilepsy or another condition that raises the risk of seizures.

If you are due to have an allergy test, loratadine may affect the result, and you might need to stop taking it a few days before.

The NHS asks you to tell your doctor if you take amiodarone for an irregular heartbeat, cimetidine for indigestion, erythromycin, or any medicine that causes sleepiness, dry mouth or difficulty passing urine, because loratadine might add to those effects. You can use paracetamol or ibuprofen alongside it, and steroid nasal sprays or eye drops for hay fever. Herbal products that cause drowsiness or dry mouth deserve a question to the pharmacist.

The NHS says it is best not to drink alcohol while taking loratadine because it can make you sleepy, although you can eat and drink normally otherwise. It does not affect contraception.

You can take loratadine in pregnancy, and the NHS describes it as one of the best antihistamine choices while breastfeeding, since only very small amounts reach milk and it has been widely used for many years without side effects in babies. Contact a healthcare professional or 111 if your baby is feeding poorly or seems unusually sleepy or irritable. There is no evidence it affects fertility.

Medicine is only part of hay fever control. The NHS suggests avoiding cutting or walking on grass, wearing wraparound sunglasses, putting Vaseline around the nostrils, showering and changing after being outdoors, vacuuming and damp-dusting regularly and avoiding smoke.