What Are Eosinophils?

Eosinophils are a type of white blood cell. There are five main types of white blood cell including eosinophils, the others are neutrophils, basophils, lymphocytes and monocytes. The primary function of white blood cells is to protect the body from invasion (infections).

Which tests include this marker?

What Role Does It Play in The Body?

Eosinophils account for up to 3% of total white blood cell count and are useful for fighting infections and help to trigger allergic responses. [1]

A high number of eosinophils circulating in the blood or eosinophilia can be an indication of infection. Commonly, eosinophils target parasitic infection particularly helminth worms. [2] They can also be an indication of an allergic reaction or cancer. When a parasite enters the body, the number of eosinophils dramatically increases. They can kill parasites including worms by releasing granular, cytotoxic proteins which cause tissue damage and dysfunction. Lab studies have shown that eosinophils can kill tumour cells, single cell micro-organisms and chicken red blood cells. In other words, eosinophils have the potential to be powerful immune cells. [3]

People who have Cushing’s disease tend to have a lower eosinophil count, particularly if they have high blood sugar. [4]

How Do Eosinophils Affect My Wellbeing?

An increase in the number of eosinophils known as Eosinophilia can occur because of a parasitic infection or an allergic reaction and so the symptoms and effects may differ. If eosinophilia is caused by asthma for example you may feel breathless or your breathing may be wheezy. These symptoms can cause you to feel anxious, lightheaded or delirious. If eosinophilia is caused by a parasitic infection you may experience the following:

  • Stomach pain
  • Diarrhoea
  • Vomiting
  • Fever
  • Skin Rashes
  • Coughing

An infection can also cause your energy levels to drop and make you feel weak and fatigued.

How Can I Improve My Result?

You may not be able to directly influence your eosinophil count but with a good lifestyle, you can improve the efficiency of your immune system.

Smoking can also damage your immune system and its response. However, some of the damage is reversible if you stop smoking. [5]


Nutrition is an important factor in our health and immune status. If we are deficient in some nutrients, then this can make our immune system weak. [6] Micronutrients including zinc, selenium, iron, copper, vitamins A, C and E, B6 and folic acid all have important influences on our immune responses. Therefore, it is essential to maintain a healthy and balanced diet incorporating all these micronutrients. [7]


Exercise is key to a healthy lifestyle. However, intense exercise can also induce immunodepression during recovery. Therefore, it is essential that you take rest periods between bouts of intense exercise to prevent illness. [8]

Tests that include this marker


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[1] Lab Tests Online UK. (2017). Eosinophils. Available at: https://labtestsonline.org.uk/glossary/eosinophil

[2] Huang, L and Appleton, J, A. (2016). Eosinophils in Helminth Infection: Defenders ad Dupes. Trends in Parasitology: 32(10), pp 798-807.

[3] Sanderson, C, J. (1992). Interleukin-5, Eosinophils, and Disease. Blood: 79(12), pp 3101-3109.

[4] Lee, Y., Yi, H, S and Kim, H, R et al., (2017). The Eosinophil Count Tends to Be Negatively Associated with Levels of Serum Glucose in Patients with Adrenal Cushing Syndrome. Endocrinol Metab: 32(3), pp 353-359.

[5] Brodin, P and Davis, M, M. (2017). Human Immune System Variation. Nature Reviews: Immunology: 17(1), pp 21-29.

[6] Kafeshani, M. (2015). Diet and Immune System. Immunopathologia Persa: 1(1).

[7] Chandra, R, K. (1997). Nutrition and the Immune System: An Introduction. American Journal of Clinical Nutrition: 66, pp 460S-463S.

[8] Peake, J, M., Neubauer, O., Walsh, N, P and Simpson, R, J. (2016). Recovery of the Immune System After Exercise. Journal of Applied Physiology: 122, pp 1077-187.

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