This article lists 11 common causes of a rash on the inner thigh, along with possible treatment options and preventive techniques.

Causes

There are many possible reasons for an inner thigh rash. Both women and men are susceptible to inner thigh rashes, although the causes may vary between the sexes.

Potential causes include:

1. Atopic dermatitis

Atopic dermatitis, more commonly known as eczema, causes red, itchy, and dry skin. The condition is more common in children, although it can occur at any age.

According to the American Academy of Dermatology Association, an estimated 10 to 20 percent of children worldwide have eczema, while just 1 to 3 percent of adults do.

Eczema may begin in the creases of the elbows or knees, but it often spreads to other areas of the body, including the inner thighs.

Over time, this skin condition may cause:

• a leathery appearance
• dry skin
• lightening or darkening of the skin
• permanent bumps

2. Chafing

The inner thighs are especially prone to chafing because they can rub against one another or be irritated by clothing and pantyhose. Physical activities, such as running, may also lead to chafing.

Chafing is characterized by redness and blistering, although these symptoms should clear up once the cause of the chafing is addressed.

3. Contact dermatitis

Contact dermatitis causes a rash to flare up following skin exposure to an irritant (irritant contact dermatitis) or an allergen (allergic contact dermatitis).

Irritant contact dermatitis may be caused by a variety of substances, including:

• bleach
• detergents
• fragrances
• soap

Allergic contact dermatitis is less common and results from exposure to substances such as:

• latex
• nickel
• poison ivy

The inner thighs may be especially prone to contact dermatitis because they come into close contact with clothing and detergents on a regular basis.

4. Heat rash

Heat rash, also known as miliaria or prickly heat, occurs when the pores become blocked and trap the sweat in the skin. Although it can be itchy and irritating, this skin rash is not dangerous.

It appears as tiny bumps on the skin and can affect any area of the body, from the back and chest to the groin and inner thighs. Symptoms usually resolve once the skin cools down.

Heat rash occurs in hot and humid environments and most commonly affects infants, children, and people on bed rest.

5. Hidradenitis suppurativa

Hidradenitis suppurative (HS) is a rare rash that presents as blackheads or pimple-like bumps under the skin, which may burst and ooze push. It occurs where skin rubs against skin, so it is common in the inner thighs, groin, and armpits.

The cause of HS is unknown, but it is most common in people who:

• have excess weight or obesity
• smoke
• have depression, anxiety, or both
• have diabetes, metabolic syndrome, or both
• have follicular occlusion tetrad, a syndrome that combines HS with acne conglobata and dissecting cellulitis of the scalp
• have squamous cell carcinoma in the affected areas

HS affects three times more women than men, and it usually begins between puberty and menopause, according to the American Academy of Dermatology.