Allergic contact dermatitis - Allergy contact dermatitis

Japanese: アレルギー性接触皮膚炎 - アレルギーせいせっしょくひふえん（英語表記）Allergic contact dermatitis

What is the disease?

When an allergen comes into contact with the skin, an allergic reaction occurs, causing itchy red spots and Papule ( Emergency ) Symptoms that only appear when the skin is exposed to light after contact are Light Contact ( Hikari Sesshoku ) It is called dermatitis.

What is the cause?

Many things can cause this, but the most common are metal products such as watch bands, accessories, and buckles, cosmetics and perfumes, plants such as sumac, hazel, and primula, hair dyes, leather products, medicinal patches, and topical medications.

Delayed ( Chiengata ) It is caused by an allergic reaction, and after repeated contact with an antigen, T cells that react to the antigen are produced in the body, causing symptoms to appear.

How symptoms manifest

Initially, symptoms such as erythema are seen only in the area where the causative substance came into contact, but gradually the symptoms spread to the surrounding skin. Symptoms do not appear immediately after contact, but several hours later, sometimes 1-2 days later, and last for several days. In addition to itchy erythema and papules, in severe cases, swelling and Blisters ( Water ) appears and leaves pigmentation behind after it heals.

In photocontact dermatitis, symptoms appear only in areas that have come into contact with the causative substance and are exposed to light. In photocontact dermatitis caused by a plaster, symptoms may also appear on areas where the patch was applied several weeks ago. In addition, small blisters and papules may appear scattered all over the body along with contact dermatitis. This is called autosensitization dermatitis and may persist even after the contact dermatitis has healed, and may take a long time to heal.

Testing and diagnosis

A patch test (a test piece) is performed in which the substance or its components suspected to be the cause are applied to the skin for 48 hours using a test bandage. In the case of photocontact dermatitis, the area is exposed to ultraviolet light after the bandage is removed. If the area turns red, it is considered positive.

Treatment methods

Antihistamines are administered orally and steroid ointments are applied. In cases where symptoms are severe, such as those caused by poison ivy or hair dye, oral steroid medication may be necessary.

What to do if you notice an illness

It is important to avoid contact with the causative substance, as symptoms may become more severe with continued contact. Be aware that even if you have no symptoms when you first start using cosmetics or topical medications, symptoms may appear with continued use, or symptoms may appear for the first time when you use them for the first time in a long time.

Michiko Aihara

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　抗原になる物質が皮膚と接触することにより皮膚にアレルギー反応が起こり、かゆみを伴う紅斑や丘疹(きゅうしん)などがみられます。接触後に皮膚に光が当たって初めて症状が現れるものを光接触(ひかりせっしょく)皮膚炎といいます。

原因は何か

　多くのものが原因になりますが、時計バンドやアクセサリー、バックルなどの金属製品、化粧品や香水、ウルシやハゼ、プリムラなどの植物、毛染め、革製品、湿布薬や外用薬などによるものが多くみられます。

　遅延型(ちえんがた)アレルギー反応によるものであり、抗原になる物質に何度か接触しているうちに抗原に反応するT細胞が体内に作られ、症状が現れるようになります。

症状の現れ方

　はじめは原因物質が接触した部分に限って紅斑などの症状がみられますが、次第に拡大して周辺の皮膚にも広がります。接触した直後ではなく数時間後、時に1～2日たってから症状が現れ、数日間続きます。かゆみを伴う紅斑や丘疹のほか、症状が著しい場合にははれや水疱(すいほう)が現れ、治ったあとに色素の沈着を残します。

　光接触皮膚炎では原因物質が接触した部分で光が当たったところにだけ症状が現れます。湿布薬による光接触皮膚炎では、数週間前に貼った部分にも症状がみられることがあります。また、接触皮膚炎に伴って全身に小水疱や丘疹が散在して現れることがあります。これは自家感作性(じかかんさせい)皮膚炎といって接触皮膚炎が治っても持続することがあり、治るまでに長期間を要することがあります。