That’s where antihistamines come in - they’re medicines that can help with allergy symptoms so you can get on with doing the things you want to do. But there are lots of different types, so how do you know which one to take? We look at how they work, what’s available - and how to get the best out of them so you can stop an allergy in its tracks.
How antihistamines work to ease allergy symptoms
Antihistamines are often used to manage
. They can also be used to relieve symptoms of
- as their name suggests, antihistamines work by blocking the effects of something called histamine
- hIstamine is a chemical that your body needs to help fight off infections. It’s released when your body comes into contact with an invading virus or bacteria. Histamine makes your blood vessels more leaky to allow more white blood cells to reach the affected area and fight the virus or bacteria
- but when you have an allergy, your body releases histamine when it’s exposed to something harmless, like pollen or house dust mites. This triggers an allergic reaction that can irritate your throat, eyes, lungs, sinuses, digestive system and/or skin
- antihistamines can stop your body releasing this histamine when it doesn’t need to. They can prevent symptoms if you take them before you come into contact with your trigger, or they can help ease symptoms once they’ve started
What type of antihistamines are there?
Antihistamines are normally divided into 2 types:
- drowsy antihistamines (also known as sedating antihistamines) – these can cross from your blood into your brain and make you feel sleepy. They may also affect your coordination, movement and concentration
- non-drowsy antihistamines (also known as non-sedating antihistamines) – these are less likely to enter your brain and tend to cause less sleepiness as a result. Some people do sometimes feel drowsy even with these antihistamines, particularly at higher doses
You can get both types of antihistamine from pharmacies. You may need a prescription to take certain antihistamines, like hydroxyzine.
Here are some of the antihistamines you can get from your pharmacist.
|cinnarizine (available in UK pharmacies but not in the US)
|promethazine (a prescription is needed in the US)
How you take antihistamines
Antihistamines also come in a few different forms. Depending on your symptoms, you can take them as tablets, capsules, liquids, topical creams, eye drops or nasal sprays. If there’s a choice of antihistamine forms for your condition, you may just be able to pick the type you prefer.
Which antihistamine is right for you?
With so many types of antihistamine to choose from, we’ve made it easier for you to find one that might suit you, depending on what type of allergy you have. Some antihistamines can work better for some people than others so you might need to take one for a few weeks to see how well it works, and try a different one if you’re still having symptoms. “It’s up to you whether you want to take a drowsy or non-drowsy antihistamine,” says
, clinical content reviewer. “If your symptoms are worse at night, you may want to take a drowsy one. Just watch out for any effects that carry over to the next morning, as some people will continue to feel sleepy for longer. If you do, don’t drive.”
Hay fever and allergic rhinitis
and other allergic conditions that affect your nose, throat and eyes are normally treated with non-drowsy antihistamines like cetirizine or loratadine. You might need to try both types of medication before you find an antihistamine that works best for you.
(urticaria) and other allergic skin conditions are normally treated with antihistamines like cetirizine, fexofenadine, or loratadine. “If you’re struggling to sleep because of an itchy skin condition like hives, your doctor may suggest you try a drowsy antihistamine,” says Dr Adiele Hoffman.
Motion sickness and nausea
Antihistamines like cinnarizine can also be used to treat nausea, motion sickness and vertigo. It’s thought they work on the part of your brain that controls nausea and vomiting.
You may find it helps to use eye drops that contain an antihistamine, such as olopatadine or azelastine, to ease discomfort. These antihistamines are fast-acting but may cause some irritation, stinging or blurred vision when you first put the drop in.
We all love our pets but can sometimes be allergic to proteins in their skin flakes (dander), urine or saliva which can end up on their hair and around the house. Taking a daily non-sedating antihistamine tablet, such as loratidine or cetirizine, can help prevent these symptoms. If sneezing or a runny nose are your main symptoms, you might be recommended an antihistamine nasal spray.
If you accidentally eat a food that triggers symptoms, antihistamines can help in milder cases. They’re unlikely to help with a significant food allergy, though. If you’re allergic to a particular food, you should avoid it at all times and carry an adrenaline auto-injector pen in case you have a
cause itching and swelling of the skin around the bite, and a non-sedating antihistamine tablet will help ease these symptoms. You can also soothe the area with hydrocortisone cream (available from your pharmacist), and try a cold compress such as a damp cold towel on the area.
How to get the most from your antihistamines
Always take your antihistamine the way your doctor or pharmacist has told you, or follow the instructions in the leaflet that comes with it. If you have any questions about which type of antihistamine to take, or whether it’s safe for you to use antihistamines with other medications you’re taking, ask your doctor or pharmacist for advice.
Make sure you know about your specific medicine
Advice on how to take antihistamines can be different, depending on which one you're using. Ask your pharmacist if you have any questions or aren’t sure how to take it. Make sure you know:
- how to take your antihistamine, and - if you’re using antihistamine eye drops or nasal sprays - how to use these the right way
- the right dose for you. This can vary depending on your age and weight so take the dose advised for you by your doctor or pharmacist
- when to take it, including how many times each day. Drowsy antihistamines are often taken at night to try to prevent daytime sleepiness
- how long to take them for
- what to do if you miss a dose
Try to avoid drinking alcohol
When you’re taking an antihistamine, especially a drowsy one,
can increase your chances of feeling sleepy. Other foods and drinks don’t usually cause problems.
Check if your existing medicines might react with them
If you already take other medicines, prescribed or from the pharmacy, check with your GP or pharmacist before taking antihistamines. Some types of cough and cold remedies already have an antihistamine in them, and you should also avoid antihistamines with some types of stomach ulcer and indigestion medicines, and with antidepressants. If you’re taking any of these medicines, your doctor will help you find other ways to manage your allergies.
Remember to take your antihistamines - top tips
We know how easy it can be to forget to take your antihistamine every day, whether it’s a pill or eye drops, but these simple tips can help:
- take it at the same time every day - such as when you’re cleaning your teeth in the morning
- leave your antihistamines in a safe place where you’ll see them, like by your toothbrush or on your bedside table
- set an alert on your phone for the same time every day to remind you to take your antihistamine
- put a reminder note where you’ll see it every day, such as on your bathroom mirror or the fridge door
How long should you take antihistamines for?
You can take antihistamines as and when you need them - for example, if you have occasional problems with an allergy, or your allergy’s seasonal, you only need to use them then. For some conditions you may need to take them every day in the long term but talk it all through with your doctor to make sure you’re on the best treatment for you.
Side effects of antihistamines
The older, sedating antihistamines are likely to make you feel sleepy. Drowsiness is listed as a common or very common side effect of antihistamines like chlorphenamine, meaning lots of people who take them could be affected - as many as 1 in 10 or more. They may also affect your coordination and concentration. If you take these, you shouldn’t drive, cycle or operate machinery - and remember, if you’ve taken one at night you may still feel drowsy the next morning. Other common side effects can include dry mouth, blurred vision and nausea.
As these don’t cross from your blood into your brain as easily, non-drowsy antihistamines won’t usually make you feel as sleepy. But drowsiness is still considered a common side effect in antihistamines like loratadine, although it’s likely to be mild. You’re more likely to feel drowsy after taking non-drowsy antihistamines if you drink alcohol with them or if you take a large dose. If you take an antihistamine and you start to feel tired or sleepy, you shouldn’t drive, cycle or operate machinery.
Other side effects are rare.
When to see a doctor
Your pharmacist can often help with queries about antihistamines but there are some times when it’s key to see a doctor.
Before you take antihistamines if you:
If your antihistamines aren’t working
If you’ve been taking antihistamines but you’re still struggling with your allergy symptoms, your doctor can help you work out the reasons why - and find other ways to get your symptoms under control. Your antihistamines might not be working because:
- you’re not taking them the right way - have a look at the instructions to check
- is causing your symptoms, not hay fever or another allergy - so antihistamines don’t work for it
- you’re taking the wrong type of antihistamine - your doctor might suggest you switch to a different type to see if it works for you
If you’re worried about side effects
Most people can take non-prescription antihistamines from the pharmacy without having any serious side effects, but you should always follow the instructions that come with your medicine, and talk to a doctor or pharmacist if you’re worried.
You should see a doctor urgently if you’re taking antihistamines and you:
- can’t pee at all
- get heart palpitations
When to call an ambulance
Call an ambulance or go to your local emergency department immediately if you have any symptoms of
- this is the most serious type of allergic reaction and can be fatal. Symptoms come on quickly after being exposed to whatever you’re allergic to (such as a type of food or an insect sting), and include:
- fast, shallow breathing or wheezing
- throat or tongue swelling
- a fast pulse rate
- clammy skin
- anxiety and confusion
- fainting or losing consciousness
Your health questions answered
###I’ve heard there’s a link between antihistamines and dementia - should I be concerned?
Some recent studies have suggested there may be a possible link between the long-term use of the older, sedating antihistamines, such as diphenhydramine, promethazine and clemastine, and the risk of developing
But try not to be worried if you’ve been taking drowsy antihistamines for a while. Most of the studies linking these medicines with dementia have looked at older people who had been taking antihistamines for a long time. They may also have had other conditions and been taking other medicines that could have raised their risk. At the moment, there isn’t solid evidence that taking these sorts of antihistamines means you’re more likely to develop dementia later in life - more studies are needed.
That said, it’s probably sensible to try to avoid these antihistamines if you can, especially in the long term - your doctor or pharmacist may suggest trying one of the newer, non-drowsy types instead (these haven’t been linked with dementia). If the drowsy antihistamines work better for you, try to only use them occasionally for short periods - for example, up to a month. It’s always important to weigh up the benefits you get from any medicine against the potential risks, so speak to your doctor or pharmacist if you have any concerns. – Answered by