Many people are allergic to things found in households everywhere, such as mould, animals and chemicals, including detergents and hair dyes.
Some people are allergic to medications such as penicillin antibiotics.
Most allergic reactions are relatively mild, but occasionally someone will react so severely to an allergen that anaphylactic shock can happen.
Once diagnosed, the most effective way to manage an allergy is to avoid the allergens that cause a reaction.
This isn’t always easy, though it is often possible to manage allergies.
If you or your child have a food allergy, you need to be careful with the meals you prepare. Always read food labels.
Keep animal allergies under control by washing pets regularly.
Keep your home damp-free and well ventilated to help manage mould allergies.
Remaining indoors when the pollen count is high will help minimise hay fever, and replacing carpets with hard flooring can help with dust mite allergies.
If you think you or your child has an allergy, outline the symptoms to your doctor – keep a diary of when and how often they happen, and what seems to trigger them.
Where there is a severe allergic reaction and the cause is not obvious, your doctor will discuss referring you for allergy testing.
These tests can include skin prick testing, blood tests and patch testing.
Allergies such as hay fever can have a real impact on those who suffer, but there are plenty of treatment options that can mean symptoms can be minimised.
It is easier to treat mild allergies that have a clear cause and many allergy medicines, such as antihistamines, are available over the counter.
But when symptoms are more troublesome, talk to your GP or online doctor who can discuss prescription-only treatment with you.
* Dr. Alexandra Phelan is a GP with the NHS and Pharmacy2U, an online service which provides free, fast and convenient delivery of NHS repeat prescriptions.