Chapter 17, Problem 1SA

Why are antihistamines useful for treating many IgE-mediated allergic reactions not totally effective in treating asthma?

Summary Introduction

To review:

The antihistamines useful for treating many IgE-mediated allergic reactions are not totally effective in treating asthma.

Introduction:

Histamines are body’s natural allergic response playing important role in allergic reactions, blood vessel dilation, and permeability of walls of blood vessels. Antihistamines are medications used to treat common allergy symptoms, such as sneezing, watery eyes, hives, and a runny nose.

Explanation of Solution

Asthma is a respiratory allergy that inflames and narrows the airway passage in lungs. When an allergen reacts with IgE-sensitized mast cells it produces degranulation and further release inflammatory mediators (leukotrienes and prostaglandins) into the lower respiratory tract. These mediators, in turn, cause immediate spasms of smooth muscle tissue lining the bronchial tubes present in lungs. This leads to increase in mucus production, which interferes with breathing. White blood cell, eosinophils mostly present at the site of infection contribute to a long-term inflammatory response.

Since, histamine is not primarily responsible for causing asthma Antihistamines are not completely effective for treatment of asthma. On the contrary, bronchodilating drugs are used which relaxes constricted muscles and relieve bronchospasm and drugs (cortisone-like steroids) are generally used to decrease long-term inflammatory reaction for asthma.

Conclusion

Therefore, antihistamines are not effective measure for treating asthma. Generally, bronchodilating drugs and steroids are useful for treating disease.