For most people the concept of being allergic to something, for example to a drug, food, or poison ivy, is not particularly hard to understand and accept. On the other hand, the idea of being allergic to yourself is a much more difficult notion to grasp. Nevertheless, a surprising number of allergies of this kind do occur. Immunologists call these reactions autoimmunity (literally, immunity against self), and allergic disorders of this variety are known collectively as autoimmune disorders.

The natural question arises: How can someone be allergic to himself or herself and still live? The fact is, many autoimmune disorders are serious and even life-threatening and require intensive medical therapy for lives to be saved. Immunologists and rheumatologists, the medical specialists most concerned with these diseases, would probably be the first to admit that while much progress has been made in diagnosis and treatment over the last quarter of a century, much more remains to be learned about autoimmune disorders.

Some of the growing list of diseases that have been associated with autoimmunity are as follows:
1. A wide variety of blistering diseases of the skin, including pemphigus and pemphigoid
2. Acute rheumatic fever, a special form of heart disease
3. Certain neurologic and muscular disorders, such as multiple sclerosis and myasthenia gravis

A detailed discussion of these and the many other conditions linked to self-allergy is well beyond the scope of this book, but in this article I hope to give you a broad overview of some of the more common conditions in this category. This includes a group of diseases known as collagen vascular disorders; two relatively common glandular conditions, Hashimoto's thyroiditis and juvenile-onset diabetes; and two well-known dermatologic conditions, vitiligo and alopecia areata.

Collagen-Vascular Disorders (Arthritic Diseases)
This category of conditions comprises a variety of diseases in which autoimmunity was first suspected and the notion articulated. It is composed of systemic lupus erythematosus (often called "lupus" or SLE for short), rheumatoid arthritis, progressive systemic sclerosis ("scleroderma"), and dermatomyositis, among others. Although each of these conditions is a distinct disease, they are grouped together because they have similar signs and symptoms and, in certain cases, overlapping laboratory abnormalities. The common manifestation of arthritis in victims of these disorders accounts for the name of the specialty that most often deals with them: rheumatology, or the study of joint diseases.