Allergic reactions


An allergic reaction is when your body's immune system overreacts to a particular substance in order to fight it off. These substances – such as pollen, pet hair, dust mites, certain foods, or materials like latex – are usually harmless to people who don't have an allergy to them. The substances that trigger allergic reactions are called 'allergens'.

Allergic reactions are very common. Around one in four of us will experience an allergic reaction at some point in our lives. They're more common in children. Some people grow out of allergies as they get older, while others experience allergies all of their lives. 

While allergic reactions are unpleasant and can interfere with our daily lives, the majority are classed as mild and can be managed with simple measures. However, a few people have extremely serious allergic reactions that can be life-threatening if not treated quickly.

Managing a severe allergic reaction

A very severe allergic reaction is known as 'anaphylaxis' or 'anaphylactic shock'. This is a medical emergency, and can be very serious, or even fatal, if not treated quickly.

Symptoms of anaphylactic shock include:

• Feeling lightheaded or faint, or even collapsing and losing consciousness

• Breathing difficulties (fast or shallow breathing, or wheezing)

• A racing heartbeat

• Damp, clammy skin

• Feeling anxious, disoriented or confused

• Other allergy symptoms (such as a rash, swelling, feeling sick or vomiting)

If the person experiencing the reaction has an adrenaline auto-injector, follow the instructions printed on the side of the device to give the injection. 

Call 999 for an ambulance immediately and tell the operator that the person may be having anaphylaxis.

Even if their reaction begins to subside once the injection has been administered, you must still call an ambulance. The reaction may return as the injection’s effect begins to wear off.

If there's a trigger for their reaction that you can remove (for example, if they have a bee or wasp sting still stuck to their skin) carefully remove it. Ask the patient to lie down, positioning pregnant women on their left side. If the person is having difficulty breathing, they should sit up to help them breathe more easily. If they are unconscious, put them into the recovery position (lie them on their side, using an arm and leg to stop them rolling, and tilt their chin to open their airway).

Common symptoms of an allergic reaction

Very few allergic reactions are as severe as the anaphylaxis described above. Allergic reactions usually cause symptoms that are annoying but manageable. These symptoms will usually occur within a few minutes of our bodies being exposed to an allergen.

Allergic reactions can affect many different parts of our body. For example, you may experience:

• Nasal symptoms such as sneezing, a runny or blocked nose, and nasal itching

• Eye symptoms such as red, itchy or watery eyes

• Breathing symptoms such as wheezing, breathlessness, coughing and tightness in the chest

• Skin symptoms such as dry, cracked, reddened skin, or an itchy, raised, red rash (hives)

• Digestive symptoms such as stomach pain, nausea or vomiting, or diarrhoea

• Swelling in your eyes, face, lips or tongue

Common allergens

Allergic reactions can be very individual and it's not possible to list every possible trigger. However, there are some allergens that many people react to:

• Grass and tree pollen (an allergy to these is also called 'allergic rhinitis' or 'hayfever')

• Dust mites

• Animal hair or dander

• Certain foods (especially nuts, shellfish, eggs, cow's milk, and certain fruits such as strawberries)

• Insect bites or stings (especially wasps and bees)

• Latex (found in protective gloves, condoms, and some school supplies such as pencil erasers)

• Mould

• Household cleaners

• Hair dyes

• Medicines, such as certain antibiotics

If you notice your symptoms come on within a few minutes of being exposed to one of these substances, it's possible you have an allergy.

How allergies are diagnosed

If you think you or your child may have had an allergic reaction to something, make an appointment to see your Doctor.

Your symptoms may have subsided by the time you see your Doctor, so it's a good idea to take photographs of any rashes or swelling, and to make a note at the time of exactly what symptoms you experience.

Your Doctor will examine you and ask you for details of your experience. This is to determine if the symptoms were due to an allergic reaction or if they were caused by some other condition

If your allergy has the potential to be severe, or if it's not clear exactly what you are allergic to, you may be referred to an allergy-testing clinic. The clinic will be able to assess which substance you're allergic to and how severe your allergy is, and can give advice on managing it. The tests conducted by the clinic may reveal that you are allergic to other substances you may not have been exposed to yet.

If you suspect you or your child have an allergy to a particular food, you may be advised to follow a food elimination diet. This involves removing the suspect food from your diet for between two and six weeks then gradually reintroducing it, with any symptoms being monitored throughout. It's important that you only undertake a food elimination diet under the guidance of a qualified and registered dietitian.

Next steps

• If you think you or someone around you may be having a severe allergic reaction (anaphylaxis), use an adrenaline auto-injector if you or the person has one and call an ambulance immediately

• If you think you or your child may be experiencing an allergy for the first time, make an appointment with your Doctor

• Your symptoms may have subsided by the time you see your Doctor, so take notes of your symptoms and photograph any rashes or hives