Any substance that we come into contact with, in our daily routine, has the potential to cause allergy.  Fortunately only some people react to those substances in an exaggerated way.  So, Allergy is an exaggerated response or reaction of the body to a substance that is not normally harmful. 

Allergy might affect different organs in the body, like the skin, lungs, abdomen, eyes and sometimes the entire body. For example, many in winter suffer from respiratory allergy in the form of continuous sneezing, watery eyes, nasal drips, etc. called Hay-fever.   There are other allergic effects like, Allergic Conjunctivitis, Food Allergy, Drug Allergy, etc.  One form of severe allergy is anaphylactic shock which is most commonly due to foods and drugs of which penicillin is infamous.  Many a time the allergy runs in the families indicating a genetic predisposition.

Allergy causing substances are called Allergens

• Allergens that are breathed in often cause a stuffy nose, itchy nose and throat, mucus production, cough or wheezing

• Allergens that touch the eyes may cause itchy, watery, red, swollen eyes.

• Eating something you are allergic to can cause nausea, vomiting, abdominal pain, cramps, diarrhea, or a severe life-threatening reaction

• Drug allergies usually involve the whole body and can lead to a variety of symptoms.

• Allergens that touch the skin can cause skin rash, hives, itching and blisters or even skin peeling.

For many people allergy manifests on the skin. The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress.There are different kinds of dermatitis, for example,  Contact  dermatitis, Atopic Dermatitis , Irritant dermatitis etc.  Dermatitis is frequently called as Eczema. 

Atopic dermatitis:
Atopic dermatitis is an itchy, chronic, fluctuating disease that is slightly more common in boys than girls. The disruption of the skin barrier has been known to  The age of onset is between 2 and 6 months in the majority of cases, but it may start at any age, even before the age of 2 months in some cases. The distribution of the eruption varies with age, as described below.

Infantile phase:
The lesions most frequently start on the face but may occur anywhere on the skin surface. Often the napkin area is relatively spared. When the child begins to crawl, the exposed surfaces, especially the knees become involved. The rashes may become infected. The disease runs a chronic, fluctuating course, varying with such factors as teething, respiratory infections, emotional upsets and climatic changes. The winter season is notorious for causing flares of atopic dermatitis.

Childhood phase:
From 18-24 months onwards the sites most characteristically involved are the elbow and knee flexures, sides of the neck, wrists and ankles. The sides of the neck develop a dark pigmentation. The reddish lesions soon turn thick and pigmented due to constant itching, this is called lichenification. Acute generalized or localized vesiculation should always suggest the possibility of secondary bacterial or viral infection

Adult phase:
                The picture is essentially similar to that in later childhood, with lichenification, especially of the folds of the elbow and knee joints and hands. Photo-sensitivity may be a feature in adult phase. Pigmentation around the lips may occur.

Allergic contact dermatitis:

                As the name suggests, this dermatitis is caused by contact with an external factor. The list of contact allergens is endless but a few common perpetrators will be discussed. It may take years of prolonged contact for a person to become sensitized to an allergen but once the reaction has occurred then subsequent exposures can cause rashes in less than 24 hours. This is because the person would have developed immunity to that particular allergen.

For example a brick layer may take 10 yrs to develop sensitivity to chromate which is present in cement. But then even after a rest period when he gets back to work he can develop the rashes within 24hrs.

Nickel dermatitis:
                Release of nickel from metal objects can cause reactions that can be quite distressing. Sometimes it bears a semblance to fungal infections and may be misdiagnosed.  Sometimes lesions may persist even if the offending object is removed.  Commonly the belt buckles, metal watch straps, button of the jeans, metal borders of mobile phones can cause sensitization and then dermatitis.

Dermatitis due to Rubber:

                This is quite common in persons wearing rubber gloves. It usually affects the dorsum of the fingers and hands. The space between the fingers may be spared. Some shoes are glued together with rubber and this may cause allergies over the feet. The instep of the sole maybe spared in this kind of eczema. Some clothing may contain rubber fittings like brassieres or caps or the elastic in underwear. Allergy to the rubber in condoms is also known.

Photo allergic dermatitis:

                These are allergies caused by chemicals which come in contact with the skin leading to sensitivity to sunlight or any UV radiation. Common agents are musk perfumes, certain pain relieving balms, some tranquilizers, sulpha drugs and ironically some components of sunscreen agents. Farmers exposed to photosensitizing plant contents can develop photodermatitis.

Irritant dermatitis:
                This is an instantaneous reaction to highly caustic substances. For example, some insects release a chemical which leads to blister formation also called piedrous dermatitis. Certain hair dyes, shampoos, detergents and acids can cause an instant eruption of redness, itching with blister formation and oozing.  Irritant dermatitis can occur to any person and is not mediated by immunity unlike allergic dermatitis.

Tests that can help in diagnosis:

As is evident, the cause of allergies is varied and finding the aggravating factor can be difficult for the doctor as well as the patient. But there are certain measures that can aid in the diagnosis of the disease and provoking elements.

Complete blood count where in there will be an elevation of the eosinophil count.

 Serum IgE levels indicate atopic dermatitis, approximately 80% of atopic dermatitis patients may show elevated levels of IgE.

 Patch tests - small amounts of possible allergens are placed onto the skin and observed for a reaction up to 48 hrs. If there is sensitivity to any of the allergen then only the particular area which was in contact with the allergen will show signs of dermatitis.  Some times the skin may need to be exposed to light to rule out photo allergic contact dermatitis.
 

Skin prick tests- similar to that of patch testing but in this case an array of allergens are pricked into the skin and observed for a reaction.

Bacteriology swabs: to know if a resistant bacteria has caused the deterioration of the eczema.

Treatment:
The treatment of dermatitis depends on the diagnosis. If there is an aggravating factor it should be avoided.     Steroid (cortisone) creams, injections and tablets are excellent medicines for quick control of the flares. There is a fear of cortisone among society but this is largely due to misinformation. If the physician’s directions are followed accordingly then there is no cause for undue concern.  If

the rashes are infected then antibiotics, either orally or as creams, have to be prescribed. Off late there are creams like tacrolimus and pimecrolimus which are relatively harmless and can be used for long term management of the disease. This helps the physician to decrease the dosage of steroids also.  The role of the humble moisturizer cannot be emphasized enough. Essentially it maintains what is known as the Skin Barrier to prevent the onset of infections and also to prevent exacerbations of eczema.

Conclusion:
                The need for a likely diagnosis and the isolation of aggravating factors are of prime importance. Strict adherence to the advice rendered by the doctor and prompt visits to the physician upon the eruption of rashes are paramount.  All these measures help to achieve a better quality of life for the person and loved ones.
 

-- Dr. Joe