How to recognise a severe allergic reaction – and when adrenaline is needed

Antihistamines, steroids, immunotherapy and epinephrine (adrenaline) may all have a role to play in allergy treatment

depending on the type and severity of the reaction. But when an allergic reaction becomes severe and life-threatening – a condition known as anaphylaxis – recognising the early warning signs and acting quickly can save a life.

In South Africa, epinephrine is more commonly known as adrenaline. It is used to treat anaphylaxis, while antihistamines are generally used for mild to moderate allergic symptoms. Understanding the difference is important, but so is knowing when to get emergency help.

“You would use an antihistamine in mild to moderate allergic reactions,” explains Dr Tshegofatso Mabelane, a family allergy specialist at Mediclinic Morningside. “Epinephrine/adrenaline is used in a life-threatening reaction that may lead to death.”

What is a severe allergic reaction?

A severe allergic reaction, or anaphylaxis, can develop quickly and may affect more than one part of the body. Symptoms can include swelling of the throat or tongue, difficulty breathing or swallowing, wheezing, dizziness, a sudden drop in blood pressure, a fast heartbeat or pulse, faintness, collapse, widespread hives, vomiting, or a sense that something is seriously wrong.

If anaphylaxis is suspected, administer adrenaline if it has been prescribed, and seek emergency medical help immediately. Even if symptoms improve after one dose, the person still needs to go to hospital, as symptoms can return or may not resolve completely after a single injection.

Understanding antihistamines

“An antihistamine is medication that works against histamine, a substance released by allergy cells during an allergic reaction,” Dr Mabelane continues. The allergic reaction occurs because your immune system reacts to something that isn’t harmful like pollen, and therefore releases histamine and other mediators, which can cause inflammation in your throat, nose, skin, lungs and so on. “Symptoms caused are mild to moderate, for example, hives in food allergy, sneezing and an itchy nose in allergic rhinitis, or itchy and watery eyes in eye allergies.”

It’s therefore appropriate to use antihistamines to block the effects of the histamine that causes immediate mild to moderate allergic reactions. Antihistamines are taken orally in the form of capsules, tablets, skin creams, nasal sprays and so on. They can be bought over the counter, and if symptoms worsen, stronger forms of antihistamine can be prescribed by your doctor. They generally take about 30 minutes to take effect.

However, antihistamines should not be relied on to treat anaphylaxis. They may help with symptoms such as itching or hives, but they do not act quickly enough to reverse life-threatening airway, breathing or circulation problems.

Adrenaline saves lives

“On the other hand, adrenaline is medication that treats a severe, life-threatening reaction, known as anaphylaxis in allergy,” Dr Mabelane says. From throat and tongue swelling and difficulty breathing or swallowing to a drop in blood pressure or a fast heartbeat and pulse, anaphylaxis may also lead to hives or other allergic reaction symptoms, which in such cases cannot be treated with antihistamines due to their severity.

Adrenaline is the first-line treatment in this type of medical emergency because it works quickly to reverse severe symptoms. It is delivered through an injection into the muscle of the outer thigh, either through an auto-injector (EpiPen), which is pre-filled with adrenaline solution and has the needle attached, or manually, through a syringe and needle.

It triggers a sudden burst of adrenaline to multiple areas of the body at the same time, and thereby acts quickly to reduce throat swelling, open the airways, and maintain heart function and blood pressure. It also halts the release of more histamine that causes these symptoms. The fact that adrenaline diverts the blood away from the skin and back to the vital organs means that it also helps to reduce hives and itching.

Be prepared if you’re at risk

If you’ve had anaphylaxis before, or you are concerned that you or your child may be at risk of a severe allergic reaction, consult a doctor or allergy specialist. An adrenaline auto-injector, such as an EpiPen, may be prescribed where appropriate, but it’s not something you simply buy over the counter and use without medical guidance. A specialist can help confirm your allergy risk, prescribe the correct device if needed, and show you exactly how and when to use it.

Being prepared also means knowing your allergy triggers, avoiding exposure where possible, wearing a MedicAlert bracelet if advised, making sure family members, caregivers, teachers or colleagues know what to do in an emergency, and checking regularly that your auto-injectors have not expired.

Always use adrenaline for anaphylaxis

In a severe allergic reaction, early adrenaline can make the difference. If you suspect anaphylaxis, use the prescribed auto-injector immediately and call emergency medical services. Don’t wait to see whether symptoms improve with an antihistamine first.

Antihistamines may still have a place in managing mild to moderate allergic symptoms, or as part of a broader allergy treatment plan, but they’re not a substitute for adrenaline in anaphylaxis. After adrenaline has been given, the person must still be taken to hospital for monitoring and further care, as symptoms may recur.