What is an allergy?
- An allergy refers to an exaggerated reaction by the immune system in response to exposure to certain foreign substances like food, pollen, dust and household chemicals.
- The response is exaggerated because these foreign substances are normally seen by the body as harmless in non-allergic individuals and do not cause a response in them.
- In allergic individuals, the body recognizes the foreign substance, and the allergic part of the immune system generates a response.
- Allergies are very common. They affect about one in five people at some point in their lives.
- They are particularly common in children. Some allergies go away as a child gets older, although many are lifelong. Adults can develop allergies to things they weren't previously allergic to.
Substances that cause allergic reactions are called allergens. Common allergens include:
- Grass and tree pollen – an allergy to these is known as hay fever (Allergic rhinitis)
Animal dander (tiny flakes of skin or hair)
Food – particularly nuts, fruit, shellfish, eggs and cow's milk
Insect bites and stings
Medication – including ibuprofen, aspirin, and certain antibiotics
Latex – used to make some gloves and condoms
Mould – these can release small particles into the air that you can breathe in
Household chemicals – including those in detergents and hair dyes
Most of these allergens are generally harmless to people who aren't allergic to them.
Symptoms of an allergic reaction
Allergic reactions usually happen quickly within a few minutes of exposure to an allergen. Although allergic reactions can be a nuisance and hamper your normal activities, most are mild. Very occasionally, a severe reaction called anaphylaxis can occur.
They can cause:
Runny or blocked nose
Red, itchy, watery eyes
Wheezing and coughing
A red, itchy rash
Worsening of asthma or eczema symptoms
Sneezing and an itchy, runny or blocked nose (allergic rhinitis)
Itchy, red, watering eyes (conjunctivitis)
Wheezing, chest tightness, shortness of breath and a cough
A raised, itchy, red rash (hives)
Swollen lips, tongue, eyes or face
Tummy pain, feeling sick, vomiting or diarrhoea
Dry, red and cracked skin
Worsening of asthma or eczema symptoms
Severe allergic reaction (anaphylaxis)
In rare cases, an allergy can lead to a severe allergic reaction, called anaphylaxis or anaphylactic shock, which can be life-threatening. This affects the whole body and usually develops within minutes of exposure to an allergen.
Signs of anaphylaxis include any of the symptoms above, as well as:
Swelling of the throat and mouth
Blue skin or lips
Collapsing and losing consciousness
Anaphylaxis is a medical emergency that requires immediate treatment.
How are allergies treated?
The best way to keep your symptoms under control is often to avoid the things you're allergic to.
For example, you may be able to help manage:
Food allergies by being careful about what you eat.
Animal allergies by keeping pets outside as much as possible and washing them regularly
Mould allergies by keeping your home dry and well-ventilated, and dealing with any damp and condensation.
Hay fever by staying indoors and avoiding grassy areas when the pollen count is high
Dust mite allergies by using allergy-proof duvets and pillows, and fitting wooden floors rather than carpets.
Medications for mild allergies are available from pharmacies without a prescription, but always ask your pharmacist or GP for advice before starting any new medicine, as they're not suitable for everyone.
They can be taken as tablets, capsules, creams, liquids, eye drops or nasal sprays, depending on the part of your body affected by your allergy.
Treating severe allergic reactions (anaphylaxis)
If you're at risk of this, you'll be given special injectors containing a medicine called adrenaline to use in an emergency.
If you develop symptoms of anaphylaxis, such as difficulty breathing, you should inject yourself in the outer thigh before seeking emergency medical help.