Eosinophils are white blood cells. Eosinophils are produced in the bone marrow and are normally found in the bloodstream and the gut lining. They contain proteins that help the body to fight infection from parasitic organisms, such as worms.

What is eosinophilia?

The term eosinophilia refers to conditions in which abnormally high amounts of eosinophils are found in either the blood or in body tissues. More than 500 eosinophils per cubic millimetre of blood are abnormal, and are called eosinophilia; this number usually amounts to more than 8% of all white cells.
In general eosinophilia arises as a response to parasites (such as filaria or helminths), or from allergy as occurs with asthma and allergic rhinitis, or in some gastrointestinal disorders that may be associated with food allergy.
A few drugs or inhaled allergens can cause inflammatory tissue changes accompanied by eosinophilia in susceptible people.

How does eosinophilia occur?

Increased numbers of eosinophils are produced to fight off allergic disease or parasitic infections. This is helpful in combating parasitic infections but not in cases of allergic diseases as they accumulate in tissues and cause damage. For example, in asthma, eosinophilia causes damage to the airways of the lung.

What are the symptoms of eosinophilia?

The symptoms of eosinophilia are those of the underlying condition. For example, eosinophilia due to asthma is marked by symptoms such as wheezing and breathlessness, whereas parasitic infections may lead to abdominal pain, diarrhea, fever, or cough and rashes.
Sneezing and nasal symptoms are common.

Medicine reactions often give rise to skin rashes, and they often occur after taking a new drug.

Rarer symptoms of eosinophilia can include weight loss, night sweats, lymph node enlargement, other skin rashes, and numbness and tingling due to nerve damage.

In India

In tropical countries like India, parasites are a common cause of eosinophilia, and there is often an association with asthma and allergic rhinitis.
Hypereosinophilic syndrome

Hypereosinophilic syndrome is a condition where there is no apparent cause for eosinophilia. In idiopathic hypereosinophilic syndrome occurs, with an eosinophil count in excess of 1500 cells per cubic millimeter of blood, and the heart or nervous system may be affected.

How is eosinophilia diagnosed?

Eosinophilia in the bloodstream is diagnosed from a simple blood test. Tissue eosinophilia is diagnosed by the examination of the relevant tissue.. Further tests may include blood tests to measure levels of antibodies, chest X-ray, CT scans of the chest and abdomen, skin or lung biopsies, examination of the bone marrow, and bronchoscopy.

Specific treatment for a parasite would necessitate first identifying the cause from a stool specimen, or from a blood specimen taken if there is fever.
If no abnormalities are found on a thorough physical exam, then no other tests may be indicated, although sometimes a biopsy of an involved organ may be appropriate. When there is evidence of skin allergy or asthma, it is usually necessary to use drug therapy.


The first line of treatment would be antihistamines. The next to be considered would be oral corticosteroids. For predominant asthma, a trial for several weeks of an inhaled steroid would be appropriate along with an inhaled bronchodilator like ventolin.

100 mg three times a day for 2-3 weeks. It is better to start the treatment after giving Albendazole/Zentel to get rid of any intestinal parasites.

Tropical eosinophilia

TPE is an immune hyperresponse to filarial infection. The syndrome includes a high eosinophil count, pulmonary symptoms and radiological changes, fever, dyspnea, and loss of weight.
Tropical pulmonary eosinophilia is reported from southern India, Sri Lanka, Malaysia, and Southeast Asia , caused by filarial parasites.