Sweat sensitivity and skin allergy

 

 

Many patients suffering from atopic dermatitis complain of itching and worsening of their rash after sweating. Many patients with atopic dermatitis have been found to have an allergic sensitivity to an as yet unidentified antigen in their own sweat. The majority of these patients develop positive skin test reactions to a 1,000 to 10,000-fold diluted preparation of their own sweat, whereas only 1% of the normal population has a similar reaction.

 

Another condition known as cholinergic urticaria has now been confirmed to be due to sweat allergy. These patients develop extremely itchy small hives on their skin when they are hot or when they exercise. The majority of these patients also have positive sweat skin test.

 

More interestingly, recent clinical studies in Japan suggest that sweat desensitization treatment might be effective for these conditions. Six Japanese patients with cholinergic urticaria underwent desensitization by intradermal injections of escalating doses of their own sweat. Five out of six patients showed significant symptomatic improvement.

 

We have started to offer sweat skin test to our patients who have symptoms of sweat allergy. In those patients with positive reactions, sweat desensitization might be a viable treatment option. This might be particularly valuable to those patients suffering from cholinergic urticaria, as there is currently no other viable treatment option for these patients except antihistamines.

Reference information: http://www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Sweat sensitivity and skin allergy

 

 

Many patients suffering from atopic dermatitis complain of itching and worsening of their rash after sweating. Many patients with atopic dermatitis have been found to have an allergic sensitivity to an as yet unidentified antigen in their own sweat. The majority of these patients develop positive skin test reactions to a 1,000 to 10,000-fold diluted preparation of their own sweat, whereas only 1% of the normal population has a similar reaction.

 

Another condition known as cholinergic urticaria has now been confirmed to be due to sweat allergy. These patients develop extremely itchy small hives on their skin when they are hot or when they exercise. The majority of these patients also have positive sweat skin test.

 

More interestingly, recent clinical studies in Japan suggest that sweat desensitization treatment might be effective for these conditions. Six Japanese patients with cholinergic urticaria underwent desensitization by intradermal injections of escalating doses of their own sweat. Five out of six patients showed significant symptomatic improvement.

 

We have started to offer sweat skin test to our patients who have symptoms of sweat allergy. In those patients with positive reactions, sweat desensitization might be a viable treatment option. This might be particularly valuable to those patients suffering from cholinergic urticaria, as there is currently no other viable treatment option for these patients except antihistamines.

Reference information: http://www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Eczema and dermatitis

Eczema and dermatitis are terms that mean skin inflammation. The two most common types of dermatitis are atopic dermatitis and contact dermatitis. Whereas the two types of dermatitis are indistinguishable pathologically, there are differences in terms of epidemiology, etiology and treatment.

Atopic dermatitis usually starts in infancy or early childhood. The basic problem with atopic dermatitis is an inborn defect in skin barrier function. The skin is an important barrier that protects us from our environment, and normally does not allow allergens to penetrate through. Genetic defects that lead to a reduction in the barrier function allow substances to penetrate the skin more easily. The defects also increase water loss from the skin, and dry skin is a characteristic of this condition. Allergens that penetrate through the skin barrier interact with Langerhan cells within the skin, which direct the immune system to develop allergic sensitivity to these substances. Infants with eczema are therefore much more likely to develop food allergy, respiratory allergy and asthma. Eczema therefore predisposes an individual to developing allergies and not the other way around as previously thought. Once the patient develops allergic sensitivity to an allergen, exposure to that allergen through direct contact or ingestion then leads to allergic inflammation in the skin. Inflamed skin is dry, intensely itchy, rough and can become infected easily. Common allergens that can cause atopic dermatitis include food, house dust mites, chemical substances found in skin care products, rubber chemicals, metals, and even sweat and bacteria that live on the skin.

Treatment of atopic dermatitis should first and foremost include repairing the skin barrier function to reduce allergen penetration. This can be accomplished by the regular use of barrier ointments. 

Food allergy is often an important factor in patients under the age of three, but diagnosing allergy in atopic dermatitis is full of pitfalls. These patients generally have very high total IgE antibody levels, rendering the use of allergy blood tests unreliable; in the presence of a large amount of IgE, non-specific IgE binding occurs and a large number of false positive reactions are seen. Many patients erroneously go on diets avoiding many foods based on these findings, whereas most patients are only allergic to less than three kinds of food. Skin prick tests are more reliable, but only if done during disease remission. Skin tests performed on inflamed skin will also result in a large number of false positive reactions. We therefore always treat the dermatitis first and do allergy tests once the disease is under control. 

Reference information:  www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Eczema and dermatitis

Eczema and dermatitis are terms that mean skin inflammation. The two most common types of dermatitis are atopic dermatitis and contact dermatitis. Whereas the two types of dermatitis are indistinguishable pathologically, there are differences in terms of epidemiology, etiology and treatment.

Atopic dermatitis usually starts in infancy or early childhood. The basic problem with atopic dermatitis is an inborn defect in skin barrier function. The skin is an important barrier that protects us from our environment, and normally does not allow allergens to penetrate through. Genetic defects that lead to a reduction in the barrier function allow substances to penetrate the skin more easily. The defects also increase water loss from the skin, and dry skin is a characteristic of this condition. 

Allergens that penetrate through the skin barrier interact with Langerhan cells within the skin, which direct the immune system to develop allergic sensitivity to these substances. Infants with eczema are therefore much more likely to develop food allergy, respiratory allergy and asthma.


Eczema therefore predisposes an individual to developing allergies and not the other way around as previously thought. Once the patient develops allergic sensitivity to an allergen, exposure to that allergen through direct contact or ingestion then leads to allergic inflammation in the skin. Inflamed skin is dry, intensely itchy, rough and can become infected easily. Common allergens that can cause atopic dermatitis include food, house dust mites, chemical substances found in skin care products, rubber chemicals, metals, and even sweat and bacteria that live on the skin.

Reference information:  http://www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

What is allergy?

An allergic reaction occurs when our immune system reacts to otherwise harmless substances from outside our body. Our immune system has an important role in protecting us from infections. It normally recognizes bacteria, viruses and fungi by reacting to their proteins (antigens), but only under circumstances that present danger to our body such as tissue damage. In the absence of such “danger signals”, foreign proteins are usually recognized as harmless and are tolerated. This process of immune tolerance occurs the first time our immune system comes in contact with these foreign proteins, such as when an infant ingests milk formula or breathes in pollens for the first time. However, if immune tolerance to a particular antigen fails to develop or is lost, the individual then becomes sensitized to this antigen and develops antibodies and specific T cells against it. An antigen that causes allergic sensitization is called an allergen. When the individual is exposed to this allergen again, an allergic reaction occurs.

Allergic symptoms can be caused by different immunological mechanisms. The majority of allergic diseases are caused by either the Type I (or immediate-type) hypersensitivity response, or the Type IV (or delayed-type) hypersensitivity response.

Immediate-type hypersensitivity reactions are caused by antibodies called IgE produced by the immune system against allergens such as pollens, house dust mites, mold spores, animal dander, insect venom, food or drugs. When the patient is exposed to these allergens, the IgE attached to allergy cells called mast cells binds to the allergens and trigger the mast cells to release chemical mediators such as histamine. This leads to swelling, itching, redness, congestion and airway constriction within a matter of minutes. Mast cells are mostly found in the skin, respiratory tract and gastrointestinal tract. IgE antibodies are involved in causing nasal and ocular allergy, asthma, insect sting allergy and some types of food allergy and drug allergy.

Delayed-type hypersensitivity reactions are caused by a type of immune cells called T cells. Each T cell specifically recognizes one allergen, and when it is exposed to this allergen, it becomes active and produces chemical mediators that cause inflammation. This type of reaction usually occurs 24 to 72 hours after allergen exposure, and tends to become chronic. Certain types of food and drug allergy, contact dermatitis and atopic dermatitis are caused by this type of reaction.

Reference information:  http://www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

藥物過敏治療 Allergen Immunotherapy in Hong Kong

Allergic diseases such as allergic rhinitis (nasal allergy), allergic conjunctivitis (ocular allergy) and asthma are chronic diseases.  These diseases are caused by the immune system reacting inappropriately to normally harmless substances such as pollens, dust mites, mold spores and animal dander.  While there are drugs such as steroids and antihistamines that can effectively control the symptoms, the only option for eliminating the root cause of the problem remains allergen immunotherapy (also called desensitization, hyposensitization or allergy shots).

Allergen extracts are prepared according to the sensitivities of the individual.  The extracts are administered at regular intervals to induce a response called immune tolerance.  The tolerance response is achieved by the production of blocking antibodies and regulatory T cells.  When this happens, the patient’s sensitivity to the allergens progressively diminishes, and symptoms also decline.  Studies have shown that after three to five years of treatment, the effectiveness persists long-term even after treatment is discontinued.

Allergic rhinitis in childhood is a risk factor for the development of asthma.  A study shows that children who received allergen immunotherapy for allergic rhinitis have 2.5-fold reduced risk of developing asthma.  This effect is still evident 10 years after treatment.

Recent studies have also shown that for a subset of patients with atopic dermatitis, where environmental allergy is a major factor in their illness, immunotherapy is effective in reducing the severity of their skin disease.

Allergen immunotherapy has traditionally been administered by subcutaneous injections. Newer forms of treatment such as sublingual immunotherapy have been developed that are more convenient, and maybe suitable for selected patients

Reference information: http://www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.