An allergic reaction occurs when your body misinterprets a harmless substance as being harmful, and reacts in an effort to protect you. While the immune system’s job is to defend against detrimental bacteria and viruses, it sometimes develops a sensitivity to innocuous substances such as pollen, grass or cat hair and sees them as a threat. These substances are referred to as allergens, or antigens, and cause the immune system to release a chemical called histamine, resulting in symptoms such as sneezing, nasal congestion and itchy eyes. To counteract these symptoms, sufferers might take medications called antihistamines.

The symptoms you experience will often correlate with which body part was exposed to the antigen. For example:

• If your eyes are exposed to an allergen they can become red, itchy, watery and/or swollen.
• If you inhale an allergen, the result could be a blocked nose, coughing, wheezing or itching of the nose or throat.
• Allergens you have ingested could cause cramping, nausea, vomiting, abdominal pain, diarrhoea, or life-threatening anaphylaxis.
• Skin contact with an allergen may cause blisters, rashes, itching or hives.

Asthma is a chronic respiratory condition caused by inflammation in the airways and air sacs in the lungs. It can develop at any age from birth.

While there is no cure for asthma, several treatments can help manage and reduce the symptoms so they do not have a big impact on the quality of life.

• Allergies to dust mites; tree and grass pollen; domestic animals including pets and birds; some foods; and mould spores can bring on attacks.
• A bout of flu or even a cold can exacerbate asthma for up to six weeks.
• Pollutants including some chemicals, cigarette smoke and car exhaust fumes can cause an attack.
• Exercise, especially in cold temperatures, can induce an attack. However, this doesn’t mean asthmatics should not exercise. In the long term, exercise is beneficial as it increases lung fitness.
• Emotions including anxiety, anger and laughter can lead to an attack.
• Drinks that use sulfur dioxide as a preservative (for example, lime and fruit squash) can trigger attacks.
• Medicines such as aspirin, certain anti-inflammatory tablets, eye drops and beta blocker blood pressure pills may aggravate asthma in adults.