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© 2006, JS Pasricha and Ramji Gupta

All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the authors and the publisher.

First Edition : 1996

Second Edition : 1999

Third Edition : 2006

Typeset at JPBMP typesetting unit

Printed at Gopsons Papers Ltd., A 14, Sector 60, Noida

Since the publication of the second edition of the Illustrated Textbook of Dermatology, this speciality has made tremendous progress in several areas. Many more diseases have been added to the list of curable diseases, and most of the treatment regimens have been standardised to near perfection. All this progress demands that the old books are revised and new schedules/regimens are incorporated. This book has therefore been rechecked thoroughly to update the new edition with the experiences and developments during this period. The essential character of this book however, that is to cater to the requirements/need of the general practitioners and the undergraduate students has been maintained. A few diseases and photographs have also been added.

With the advances made in the field of dermatology during the last few decades, it has become possible to treat and possibly cure several diseases which till recently were considered to be incurable. This has led to a large number of patients seeking dermatologic advice and this figure is expected to go up in future because a dermatologic patient not only expects his/her disease to be controlled but also to get rid of the marks and scars left behind by the disease process. And over the years, the dermatologists have developed several techniques to achieve these objectives too.

Skin is one of the most important organs of the body because it protects the internal organs from the deleterious environmental influences. No individual can survive if the skin is not intact. The environmental agents which can influence the skin can be categorized into: (1) physical agents such as trauma, friction, extremes of heat and cold, and radiations especially sunlight, (2) chemical agents such as strong acids and alkalis which may burn the skin or lead to irritant dermatitis as with certain chemicals from the plants or incite allergic reactions as with most other chemicals, and (3) biological agents which include a variety of infecting/infesting organisms which can thrive on the skin and produce disease. The skin has several inbuilt mechanisms for interacting with the environmental agents and most of the times the skin is able to protect itself from these agents. The protective ability however, may not always be able to deal with the environmental stimulus and this leads to the production of skin disease. Since the intensity of the environmental agent is likely to vary from time to time and so also the ability of the body to protect itself, a disease is likely to result whenever the protective ability is less than the intensity of the environmental agent. In addition, some individuals may be born with a defective ability to protect themselves, and such individuals succumb to the environmental agent more easily and more frequently than the others. The aetiopathogenesis of skin diseases therefore, is based on an interaction between the nature and the intensity of the environmental agent(s) and the ability of the individual to protect himself from these influences. The protective ability of an individual is influenced by a variety of factors which include; genetic defects, nutritional deficiencies, poor hygiene, over-crowding, co-existence of other diseases and intake of certain drugs.