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Why does my skin itch? – 5 common causes of itchy rash

Why does my skin itch? – 5 common causes of itchy rash

It’s that time of year again when itchy skin becomes a problem. As an allergist, I see many patients with the complaint of “itchy rash”. But allergies are not always to blame. The first question I ask is “is there a rash?” An itch without a rash is rarely caused by allergies.

The next question is about the appearance of the rash. Is it red only, bumpy red, or does it look like “mosquito bites” which would suggest “hives”. Or is it oozing and crusting, which may suggest a contact allergy (like poison ivy).

Then how about the distribution of the rash on the body? The location of the rash helps us get a better idea about what may be causing it.

So what is the cause? Here are the 5 most common reasons for skin itch:

1. Dry Skin

This is probably the most common cause of an itchy skin rash. The rash resulting from dry skin often appears on the legs, arms and looks bumpy and may feel a little like sandpaper. It worsens when scratched and can start bleeding after a lot of scratching. Using mild soap such as Cetaphil and applying moisturizer immediately after every shower or bath helps to avoid dry skin and itch. It typically gets worse during the winter months when the air is dryer or when exposed to chlorine water frequently (swimmers).

2. Atopic Dermatitis – Eczema

Eczema usually starts in childhood and can continue into adulthood. It comes and goes, and may heal up completely at times. Eczema usually gets worse in the winter. It is typically located in the flexor area of legs or arms (behind the knee, in elbow area, wrists, ankles) and can be in the face of small children. Diaper area and moist areas (such as armpits, groin) are usually spared. Typically presenting as a bumpy, dry red rash, it can get irritated by scratching and can leave hypo- or hyperpigmentation (lighter or darker skin) and thickened skin after healing.

Good skin care is essential in dealing with eczema. Using mild soap and emollients is very important, but in addition topical corticosteroids (like hydrocortisone) may be necessary. Atopic dermatitis may have an allergic origin. Young children often have food allergies (egg, peanut) making the eczema worse. An allergy to dust mite, animals, or pollen can also contribute to exacerbations. Skin testing can be helpful to identify the causing allergen and targeted avoidance may reduce the need for steroid creams.

3. Contact Dermatitis

Contact dermatitis usually presents with a localized red oozing rash. It could start out with bumps which then become blisters and is very itchy. The location of the rash may point to the offending allergen. (If it’s in the diaper area, baby wipes may be the cause. A location on the hand of hair dressers or cosmeticians points to coloring or cosmetic agents as the cause). To find the cause, an appointment with an allergist (who can do a patch test) may be helpful. Treatment consists of a strong steroid cream in addition to avoiding the causative allergen.

4. Hives

Itchy wheals which usually look pale and can take on all kinds of shapes. Sometimes, they are lines or patterns; in that case, we talk about “dermatographism” (writing in the skin). There is a Brooklyn based artist, Ariana Page Russell, who actually turned her condition of dermatographism into a unique art form. Hives are usually harmless but very annoying. They can appear all over the body and sometimes cause swelling of the lips and eyes. Hives can be caused by food allergies, drug allergies or environmental allergies. However in most cases they are “idiopathic” – which means we are unable to find a cause. Sometimes hives appear as a consequence of autoimmune conditions such as Thyroid autoimmunity (Hashimoto thryroiditis or Graves disease), hepatitis, Lupus or hematologic conditions (lymphoma – rare). Treatment is based on avoidance when possible and antihistamines (Zyrtec, Allegra, Benadryl etc).

5. Viral Rash

Many viruses such as cold viruses or gastrointestinal viruses (Coxsackie virus, adenovirus, parvovirus) can cause rashes. This is actually the reason why so many people are thought to have a penicillin allergy. They receive treatment for a febrile illness (most commonly caused by a virus), develop a rash, and – of course – they blame it on the penicillin. In any case, most viral rashes will disappear by themselves. Symptomatic treatment with antihistamines to remove the itch may be helpful.

Finally, what if there is no rash? The “itch without rash” requires further investigation into internal origin such as hepatitis, gall bladder, or renal disease.  Lab work may be helpful to identify the cause.

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