Medicines for Raised eosinophils (eosinophilia)

What it is

Eosinophilia means a higher-than-normal number of eosinophils — a type of white blood cell — in the blood, usually found on a routine blood test (full blood count). Eosinophils are part of the immune system and are particularly involved in allergic reactions and in responding to certain infections (especially parasites). A raised eosinophil count is therefore usually a clue pointing to another condition, rather than a disease in its own right. Common causes include allergic conditions (such as asthma, hay fever, eczema, and food or drug allergies), reactions to certain medicines, and parasitic infections (particularly relevant after travel to some areas). Less commonly, eosinophilia can be associated with a range of other conditions, including certain skin, lung, and autoimmune conditions, and, rarely, some blood disorders or other serious conditions, particularly when the count is very high or persistent. Mild eosinophilia is common and often due to a benign, identifiable cause. The approach is to interpret it in context and, where needed, look for the underlying cause.

How it is treated

When eosinophilia is found, the approach is to consider and look for the underlying cause rather than to treat the count itself. A doctor takes into account the clinical picture — for example a history of allergies or asthma, medicines, symptoms, and any relevant travel — and the degree of the eosinophilia. Mild eosinophilia with an obvious explanation (such as known allergies or asthma) may need little more than managing that condition, and the count is sometimes simply rechecked. Where the cause is not clear, or the count is significantly or persistently raised, further assessment is arranged — which may include reviewing medicines, tests for parasitic infection (particularly after relevant travel), and other investigations depending on the clinical picture; a very high or persistent eosinophil count, or one with unexplained symptoms, may prompt referral to a specialist (such as a haematologist) to look for less common causes. Treating the underlying cause — for example managing the allergic condition, stopping a responsible medicine, or treating a parasitic infection — usually resolves the eosinophilia. The reassuring message is that raised eosinophils are usually a clue to another, often benign and treatable, condition, and identifying and treating that cause is the key.