How do allergies start or develop?
Are allergies such as hayfever genetic?
Most allergies are inherited which means they are passed down from parent to child.1 Although someone may inherit the tendency to be ‘allergic’, they may not inherit an allergy to the same thing.1 For example, a parent may be highly sensitive to animal dander, whereas their child may react to airborne pollens. If one parent has an allergy, their offspring have a 50% chance of developing allergies themselves. If both parents are allergic, this risk jumps to 75%.1 While there is definitely a genetic predisposition to hayfever, other risk factors include exposure to second‐hand cigarette smoke and having other allergies like food allergies or eczema.2
How does an allergy occur?
Allergies begin when a person’s immune system mistakenly identifies a normally harmless substance as dangerous and in response launches a response. When an allergen is found, for example pollen,
the immune system makes special antibodies called Immunoglobulin E (IgE) that trigger the release of histamine and other inflammatory substances, which are responsible for the uncomfortable allergy symptoms. In the case of hayfever, this immune response causes:2
- A stuffy or runny nose
- Red, itchy and watery eyes
- Swollen eyelids
- Itchy throat, mouth ears or face
- Post‐nasal drip
- Headaches, facial pain or pressure and
The immune system does not typically trigger an allergic response the first time the body encounters an allergen, but builds up a sensitisation over time.1 Once sensitised however, IgE antibodies quickly detect allergens and spring into action.1
Can allergies develop at any age?
Although allergies are more common in children, they can develop at any time or age.3? Exposure to allergens when your body’s defences are weak, like after illness or pregnancy, can sometimes trigger allergies.4
Do allergies stick around for life?
Not always. It is estimated that 80% of children with hayfever will still have trouble ten years on and 40% of young adults with allergies will still be sneezing twenty years later.4 Sometimes allergy symptoms start in childhood, disappear for many years, and then start up again in adult life.5 Unfortunately allergic people are also prone to developing new allergies,5 so while you may not be as sensitive to pollen anymore, moulds or dust mites may begin to cause difficulties.