Allergy to environmental agents can affect almost every organ of the body. Although allergic rhinitis is the commonest manifestation, the lower respiratory tract, the conjunctiva, the skin, and the gastrointestinal tract are frequently affected by allergic disease. #### Age when certain allergies are likely to occur for first time Allergic diseases are common, and their prevalence is increasing. Accurate diagnosis of triggering or causative allergens is essential for appropriate advice for avoidance and environmental control measures. Although allergic diseases can occur at almost any age, some allergies are most likely to develop for the first time in particular age groups. #### Taking a clinical history An immediate relation between exposure to potential allergens and the development of symptoms makes both the diagnosis and identification of allergy straightforward. In …