Symptoms of an allergic reaction usually develop within a few minutes of being exposed to something you're allergic to, although occasionally they can develop gradually over a few hours.
Although allergic reactions can be a nuisance and hamper your normal activities, most are mild.
Very occasionally, a severe reaction called anaphylaxis can occur.
Main allergy symptoms
Common symptoms of an allergic reaction include:
- 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
The symptoms vary depending on what you're allergic to and how you come into contact with it.
For example, you may have a runny nose if exposed to pollen, develop a rash if you have a skin allergy, or feel sick if you eat something you're allergic to.
See your GP if you or your child might have had an allergic reaction to something. They can help determine whether the symptoms are caused by an allergy or another condition.
Read more about diagnosing allergies.
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 something you're allergic to.
Signs of anaphylaxis include any of the symptoms above, as well as:
- swelling of the throat and mouth
- difficulty breathing
- blue skin or lips
- collapsing and losing consciousness
Anaphylaxis is a medical emergency that requires immediate treatment.
Read more about anaphylaxis for information about what to do if it occurs.
Page last reviewed: 22 November 2018
Next review due: 22 November 2021