What to do if you overdose on allergy pills

Most people can safely take antihistamines.

But speak to a pharmacist or your GP for advice if you:

Some antihistamines may not be suitable in these cases. Your pharmacist or doctor can recommend one that’s best for you.

Always read the leaflet that comes with your medicine to check it’s safe for you before taking it or giving it to your child.


Find out more about your medicine

If you no longer have the leaflet that came with your medicine, you can search for an online version of it on the following websites:

The leaflet will own detailed information about your specific medicine, including how to take it and what side effects you might get.

Sheet final reviewed: 7 March 2017
Next review due: 7 March 2020

Chlorpheniramine comes as a tablet, a capsule, an extended-release (long-acting) tablet and capsule, a chewable tablet, and a liquid to take by mouth.

What to do if you overdose on allergy pills

The regular capsules and tablets, chewable tablets, and liquid are generally taken every 4 to 6 hours as needed. The extended-release (long-acting) tablets and capsules are generally taken twice a day in the morning and evening as needed. Follow the directions on your prescription label carefully, and enquire your doctor or pharmacist to explain any part you do not understand.

What to do if you overdose on allergy pills

Take chlorpheniramine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Chlorpheniramine comes alone and in combination with fever and pain reducers, expectorants, cough suppressants, and decongestants.

What to do if you overdose on allergy pills

Enquire your doctor or pharmacist for advice on which product is best for your symptoms. Check nonprescription cough and freezing product labels carefully before using 2 or more products at the same time.

What to do if you overdose on allergy pills

These products may contain the same athletic ingredient(s) and taking them together could cause you to get an overdose.This is especially significant if you will be giving cough and freezing medications to a child.

Nonprescription cough and freezing combination products, including products that contain chlorpheniramine, can cause serious side effects or death in young children. Do not give these products to children younger than 4 years of age. If you give these products to children 4-11 years of age, use caution and follow the package directions carefully.

If you are giving chlorpheniramine or a combination product that contains chlorpheniramine to a kid, read the package label carefully to be certain that it is the correct product for a kid of that age.

Do not give chlorpheniramine products that are made for adults to children.

Before you give a chlorpheniramine product to a kid, check the package label to discover out how much medication the kid should get. Give the dose that matches the child’s age on the chart. Enquire the child’s doctor if you don’t know how much medication to give the child.

If you are taking the liquid, do not use a household spoon to measure your dose.

What to do if you overdose on allergy pills

Use the measuring spoon or cup that came with the medication or use a spoon made especially for measuring medication.

If you are using the extended-release tablets or capsules, swallow them whole. Do not break, crush, chew, or open them.


Taking antihistamines with other medicines, food or alcohol

Speak to a pharmacist or your GP before taking antihistamines if you’re already taking other medicines.

There may be a risk the medicines could affect each other, which could stop either from working properly or increase the risk of side effects.

Examples of medicines that could cause problems if taken with antihistamines include some types of:

It’s best to avoid alcohol while taking an antihistamine, particularly if you’re taking an older type of antihistamine, as this can increase the chances of it making you feel sleepy.

Food and other drinks don’t affect most antihistamines, but check the leaflet that comes with your medicine to make sure.


Side effects of antihistamines

Like every medicines, antihistamines can cause side effects.

Side effects of older types of antihistamines can include:

  1. blurred vision
  2. dry mouth
  3. sleepiness (drowsiness) and reduced co-ordination, reaction speed and judgement – don’t drive or use machinery after taking these antihistamines because of this risk
  4. difficulty emptying your bladder

Side effects of non-drowsy antihistamines can include:

  1. feeling ill
  2. dry mouth
  3. headache
  4. drowsiness – this is less common than with older types of antihistamines

Check the leaflet that comes with your medicine for a full list of possible side effects and advice about when to get medical help.

If you ponder your medicine has caused an unwanted side effect, you can report it through the Yellow Card Scheme.


How antihistamines work

Antihistamines work by stopping a substance called histamine affecting the cells in your body.

Histamine is a chemical released when the body detects something harmful, such as an infection.

It causes blood vessels to expand and the skin to swell (known as inflammation), which helps protect the body.

But in people with allergies, the body mistakes something harmless, such as pollen, for a threat.

What to do if you overdose on allergy pills

It then produces histamine, which causes symptoms such as rashes, a runny nose and/or sneezing.

Antihistamines assist stop this happening if you take them before you come into contact with the substance you’re allergic to. Or they can reduce the severity of symptoms if taken afterwards.


How to take antihistamines

Take your medicine as advised by your pharmacist or doctor, or as described in the leaflet that comes with it.

Before taking an antihistamine, you should know:

  1. how endless to take it for – some types can be used for a endless time, but some are only recommended for a few days
  2. when to take it – including how numerous times a day you can take it and when to take it (older types should be taken before bedtime)
  3. how much to take (the dose) – this can vary depending on things such as your age and weight
  4. how to take it – including whether it needs to be taken with water or food, or how to use it correctly (if eye drops or a nasal spray)
  5. what to do if you miss a dose or take too much (overdose)

The advice varies depending on the exact medicine you’re taking.

If you’re not certain how to take your medicine, enquire your pharmacist.


Types of antihistamine

There are many types of antihistamine.

They’re generally divided into two main groups:

  1. older antihistamines that make you feel sleepy – such as chlorphenamine, hydroxyzine and promethazine
  2. newer, non-drowsy antihistamines that are less likely to make you feel sleepy – such as cetirizine, loratadine and fexofenadine

They also come in several diverse forms – including tablets, capsules, liquids, syrups, creams, lotions, gels, eye drops and nasal sprays.

Which type is best?

There’s not much evidence to propose any particular antihistamine is better than any other at relieving allergy symptoms.

Some people find certain types work well for them and others do not.

What to do if you overdose on allergy pills

You may need to attempt more than one type to discover one that works for you.

Non-drowsy antihistamines are generally the best option, as they’re less likely to make you feel sleepy. But types that make you feel sleepy may be better if your symptoms affect your sleep.

Ask a pharmacist for advice if you’re unsure which medicine to attempt, not every antihistamines are suitable for everyone.


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What to do if you overdose on allergy pills