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Rash on Inner Thighs

Rash is a generalised term that means an area of altered skin, differing in appearance and texture from that which is physiologically normal. Skin lesions are classified into primary and secondary lesions depending upon their typical features. But the term ‘rash’ can be used to imply the occurrence of any of these lesions as a tender erythematous and/or pruritic cluster.


Skin rash often is a symptom of an underlying disease than a disease entity in itself. Thus its onset, spread, distribution and characteristics aid diagnosis. Most of the common varieties resolve spontaneously and are amenable to home treatment but a few might necessitate medical attention.

Rashes can occur all over the body surface or may be localized to a specific area. Localized skin rashes are most common in skin folds, areas which are more exposed to friction and perspiration like inner thighs. Though there are no reliable data for prevalence or incidence of inner thigh rash, it is a frequently encountered benign skin disorder.

Causes of Rash on Inner Thighs

Rash on inner thigh can occur due to numerous causes. It may be a part of systemic manifestation of a disease or maybe an isolated entity. There is considerable gender variation in its etiology. Similarly causative factors in infants differ from those in adults.

It will be prudent to discuss clinical presentation & diagnosis along with etiology as rash in general cannot be attributed any specific signs and symptoms nor it makes sense to try and diagnose it without taking into consideration associated factors. Signs and symptoms are due to and characteristic of the underlying disorder. Hence diagnosis should be tailored to individual case and investigations should be sought accordingly.
Etiology can be discussed under two broad headings- Infectious and non-infectious

Non Infectious Causes

Due to excessive heat induced perspiration

Rashes which have a heat-related etiology are termed as heat rash/sweat rash/Miliaria. Miliaria can be of the following types:

Miliaria crystallina or sudamina – Superficial clear blisters/vesicles which are fragile to touch and appear as tiny drops of water on the skin surface.

miliaria crystallina or sudamina

Miliaria rubra or prickly heat– Erythematous pruritic papules which are present in the epidermis.

prickly heat rash on inner thighs

Miliaria profunda – Erythematous pruritic papules but these are found in the dermis resulting in more severe itching than in prickly heat. These occur when sweat trickles into the dermis (middle layer of skin below epidermis).

miliaria profunda thighs

Miliaria pustulosa – erythematous pruritic pus filled blisters/pustules which might arise either in epidermis or dermis. These develop when bacterial infection is superimposed on existing Miliaria.

miliaria pustulosa on inner thighs

Miliaria develops when ducts of sweat producing glands found in the epidermis (i.e. the uppermost layer of skin) become obstructed. It is the end result of excessive perspiration which does not evaporate soon enough. Hence the common predisposing factors include:

  • Hot and humid weather – Though up to 30% of population exposed to such climatic conditions might develop heat rash; individual susceptibility varies with young children and infants being most affected. Also geriatric population, people with increased BMI (body mass index >30) and people who work outdoors in the heat are most at risk.
  • Improper clothing – tight fitting apparel especially of thick synthetic material which prevent evaporation of sweat. For example- women who wear skinny jeans have high risk of developing heat rashes on inner thighs. Similarly use of rubber, latex in clothing, elastic fittings in underwear and baby diapers predispose to development of rashes not only due to lack of proper ventilation, but also due to allergy and chafing.
  • Application of heavy creams, lotions and ointments which clog the duct openings.
  • Independent areas of bed-ridden patients which when infected may produce bed-sores. Hence Miliaria is commonly found on the backs of patients admitted in hospital wards, who are obliged to remain prone for long stretches of time e.g. post surgery, comatose patients, post stroke paralysis patients etc.
  • Activities which result in excessive sweating like running/jogging, cycling and professional sports can lead to development of sweat rash and a special type of acne called acne mechanica due to excessive sweating & skin chafing due to friction between apposing skin or between skin and ill-fitting sports apparel/accessory. For example frequent use of football pads might cause rashes on inner thighs.
  • Finally lack of hygiene – infrequent bathing leads to accumulation of sweat residue on skin. Sweat contains different types of salts and it gets mixed with an oily secretion (sebum) produced from sebaceous glands. The oil and salts do not evaporate and unless washed away, remain on the skin which can also cause obstruction of sweat gland ducts. Hence it is advised to shower daily especially when there is excessive perspiration.

Diagnosis of Miliaria can be easily made through clinical presentation alone and no investigations are needed.

Allergy

Allergic rashes, also known as hives/urticaria can occur all over the body. These form one of the major causes of inner thigh rash. Around 20% of the general population will develop hives at some point in their lives. It can occur in any of the following ways:

Allergy due to food or medication – Common food items which can cause allergy are- seafood including shrimps & crab, nuts like peanuts, almonds, walnuts, egg etc. Drugs which can cause eruption of rashes are- antibiotics(penicillin and sulpha drugs), anti-inflammatory and analgesics like Ibuprofen, Naproxen, Aspirin, Codeine; Seizure medication etc.

Irritant contact dermatitis can be in response to accumulated body fluids like sweat, urine or chemicals like rubber, latex in undergarments, chemicals in detergents used to wash underwear or those in bathing soaps/gels, irritant substances in cosmetics; touching poison oak/ivy plants or even pets. In this type of dermatitis, rash is limited to the area exposed to the irritants which might be the inner thighs.

allergic contact dermatitis on inner thighsAllergic Contact dermatitis of left (A) and right (B) inner thigh

Insect or animal bite – Honeybees, hornets, wasps, yellow jackets and fire ants. These are the insects whose venom can cause an allergic reaction in individuals stung by them. The rashes may be localised to the area of bite or may spread to other areas depending upon the severity of allergy. Also mosquitoes and bedbugs can cause itchy erythematous papular eruptions, usually clustered together which disappear after few hours.

rash on inner thighs insect bite

Again for any of the above allergies, diagnosis can be done relying solely on clinical picture.

Miscellaneous Non-infectious Causes

Seborrheic dermatitis or seborrhea produces erythematous pruritic whitish flaky rashes which can be confused with psoriasis. Though it is not very important to distinguish the two conditions during diagnosis as their management is quite similar, few differences may be used for identification.

Usually psoriatic scales are thicker and drier in appearance when compared with those in Seborrheic dermatitis. Also psoriasis affects more than one area of the body unlike seborrhea which is localized to one area at a time. Commonly affected sites are  scalp (dandruff), neck, upper chest & back, skin folds, groin (inner thighs) and buttocks. Its etiology is not exactly known but it seems to occur as a result of a combination of several factors: Stress, genes, environment (cold, dry climate), medications and yeasts that normally inhabit the skin but turn pathogenic under suitable circumstances. But it is not a form of allergy. It is common in neonates and adults aged 30-60 years & has a predilection for males. Risk factors are diverse ranging from oily skin & acne to AIDS and Parkinson’s disease. Diagnosis is mainly clinical plus a biopsy of skin scrapings to rule out Psoriasis & eczema.

Systemic diseases which produce rashes might also involve the thighs but will not usually be limited to the thighs. Such diseases include autoimmune disorders like psoriasis which produces dry scaly erythematous eruptions and inner thighs are a commonly affected site. Disease specific diagnostic protocol should be followed taking into account both local & systemic manifestations of the autoimmune disease.

psoriatic scale on inner thigh

Razor shaving of hair on inner thighs can also produce rashes especially if repeated vigorously on unsoftened hair. This problem is frequent in women and diagnosing is based on accurate history taking.

rash on inner thighs razor bumpsReddened tender rashes on shaved inner thighs

Hidradenitis suppurativa (affects 1% of the population especially young females) – It is a chronic inflammatory condition which develops due to blockage of hair follicles secondary to a number of ill understood factors including genetics, hormonal imbalance, stress, smoking and increased BMI. It is common in areas with high density of hair follicles like armpits, groin and anal area & in areas undergoing constant friction like inner thighs, under breasts or between buttocks. A single area or multiple areas may be affected.

The disease presents as – blackheads either in pairs or a “double-barrelled” pattern, red tender pus filled vesicles which often enlarge & drain pus, tender small hard lumps under skin that persist chronically or may enlarge when inflamed and finally scars of healed lesions.

rash on inner thighs pictures

Unless it affects and blocks lymphatic drainage or has severe symptoms, it usually has a very benign course. Clinical diagnosis is sufficient but pus culture may be done.

Rare Causes

Pigmented Purpuric Dermatosis like Schamberg’s disease (Non pruritic progressive pigmentary Dermatosis) – conditions of unknown etiology which cause pigmented brown (due to capillaritis, RBC extravasation into skin & Haemosiderin deposition) rash like lesions on lower limbs (legs>thighs). Diagnosis is through clinical evidence supported by dermoscopy and skin biopsy findings.

Before proceeding with infectious etiology, a condition called Intertrigo (intertriginous dermatitis) which occurs due to interplay of both inflammatory and infectious causes, should be discussed. It causes erythematous inflamed rashes on flexural skin including groin and inner thigh area. It is common in obese people and diabetics.

Inflammation can be due to genetic tendency or hyperhidrosis (increased sweating) secondary to environmental factors. Skin folds have high surface temperature, are exposed to constant friction & skin chafing and finally there is decreased evaporation of sweat.Under such conditions, the normal micro biome of skin turn pathogenic. Hence intertrigo frequently becomes infected. Though often disease due to infection and plain inflammation are almost similar, they can be segregated depending upon a few pointers- Infectious disease usually presents as unilateral and asymmetrical whereas in inflammation rashes usually are bilaterally symmetrical.

Diagnosis of intertrigo rash depends upon investigations done to enunciate the etiology of intertrigo itself- microscopy and demonstration of bacterial or fungal agents through culture, ± skin biopsy & histopathology.

Infectious Causes

Non Sexually Transmitted Infections

A) Bacterial infections

Folliculitis – It a quite common infection of hair follicles of skin resulting in clusters of tender pruritic erythematous pus filled pimple-like vesicles around hair follicles. Folliculitis may be superficial or deep. Of all its types, the ones commonly encountered in inner thighs are-

Deep Folliculitis

Boils (furuncle) and carbuncles (collection of boils) – Both occur secondary to deep follicular infection by staphylococcus aureus. Usually small boils heal without scarring but larger ones and carbuncles may scar.

Superficial Folliculitis

  • Pseudofolliculitis Barbae (barber’s itch) – common in people who get bikini waxes. It occurs due to inflammation produced by ingrowing hairs.
  • Hot tub/ Pseudomonas Folliculitis – as the name implies it is a pseudomonas infection of hair follicles and the infection is contracted usually in ill-maintained hot tubs and heated pools.

Clinical based diagnosis may sometimes be substantiated by a pus swab culture and rarely skin biopsy.

B) Infections by fungi and parasite

Fungal rash on inner thighs are commonly called jock itch/ Dhobi’s itch/ Ringworm of the groin. Medically the infectious agent is Tinea cruris, a dermatophyte which resides normally on skin but starts multiplying in warm and moist skin conditions. This male predominant {but also seen in women when they have obesity, diabetes and poor personal hygiene} infection affects skin folds of groin (genitals are spared), inner thighs, perineum and buttocks. It presents as inflamed, with or without smelly discharge, reddish brown pruritic and/or tender ring lesions (hence the name ‘ringworm’) whose symptoms exacerbate on friction. It is a contagious disease and spread is usually through sharing of undergarments and bathroom towels. Diagnosis is made on basis of characteristic symptoms, location and history of lesions. If needed a specimen of scale scrapings may be obtained for microscopic examination.

Repeated exposure to immature larvae (cercariae) of Schistosomes (a parasitic flatworm) present in infested water may produce typical skin rashes, commonly known as swimmer’s itch/cercarial dermatitis, due to body’s allergic reaction.

First exposure may go unnoticed but subsequent exposures produce within minutes/days, short-lived reddish blisters on exposed body parts including inner thighs and the symptoms worsen with each exposure. There is no commonly available and acceptable diagnostic tool. Skin biopsy has no use here. So diagnosis is merely clinical.

Various systemic infections which produce skin rashes may also be the cause of inner thigh rash- e.g. measles, chicken pox, shingles etc.

Sexually Transmitted Diseases

When STDs are the reason behind inner thigh rash, the rash usually extends to genitals and might involve other surrounding areas as well. Agents that can cause sexually transmitted rashes include:

  • Genital Herpes – Herpes simplex virus infection produces erythematous tender, pruritic vesicles which rupture into oozing/bleeding ulcers. The sores are highly contagious and infection spreads during sexual contact through small breaks in skin or mucosa. Associated features include enlarged tender lymph nodes, dysuria and systemic flu-like manifestations.
  • Genital warts – Human papilloma virus (HPV) infection causes itchy, grey or flesh coloured wart or several warts clustered together to form cauliflower shaped growths which bleed during coitus. Common in women.
  • Secondary Syphilis develops 3-6 weeks after primary syphilis/ chancre (genital sore) and is characterised by development of erythematous penny sized sores all over the body including inner thighs, palms and soles. It is associated with fever, fatigue and inguinal lymph node swelling. It may subside spontaneously or recur or may progress into latent and finally tertiary syphilis resulting in fatal complications.

To diagnose STD inner thigh rashes, the same syndromic approach is followed as done for genital rash and investigations ordered should be according to the protocol guidelines.

Causes of Inner Thigh Rash in Infants

Diaper/nappy Rash – Occurs when there is skin irritation due to accumulated urine/faeces in diapers which are not routinely changed. It presents as tender reddish rashes in the form of either vesicles or pustules which ooze on rupture, located in the diaper area i.e. perineum, genitalia, buttocks and upper inner thighs. Diagnosis is based on history and physical examination of the baby.

Other systemic diseases which may produce rashes on inner thighs include-Atopic dermatitis (dry scaly & ± itchy), Impetigo (reddish rashes that rupture, ooze and heal with yellowish brown crusting) and it’s less common variant bullous impetigo (large vesicular rashes common on diaper areas and trunk) etc. Diagnosis is disease specific.

Inner Thigh Rash in Pregnant Women

In addition to all the causes mentioned above, there are a few typical factors which can produce inner thigh rashes in pregnant women. Those include:

Physiological

Striae gravidarum/ stretch marks which are reddish purple bands of wrinkled skin that persist for long time even post delivery, located commonly on abdomen, thighs and buttocks of fair-skinned pregnant ladies.

Pathological rashes

  • Pruritic Urticarial Papules and Plaques of Pregnancy (PUPP) or polymorphic eruption of pregnancy develops in 3rd trimester as itchy reddish rash that look like hives in 0.5-1 % of pregnant ladies and then spontaneously remits post delivery without ever affecting the baby.
  • Prurigo of Pregnancy (1 in 300 pregnancies) causes small itchy rashes which resemble insect stings and may occur anywhere including inner thighs. Unknown etiology and no treatment usually needed.
  • Impetigo herpetiformis is a rare non-pruritic pustular rash of groin and inner thigh areas which may spread to other body parts and also produce systemic symptoms of nausea, vomiting, diarrhoea, fever and lymphadenopathy. Though its exact etiology is still undecided, it is known to harm the foetus indirectly through placental insufficiency and hence medical attention in required.
  • Pemphigoid gestationis/herpes gestationis is a rare autoimmune disorder of 2nd/3rd trimester pregnancy which presents as erythematous pruritic vesicles on limbs including inner thighs and abdomen. Infants of affected ladies may develop rash in 5-10% cases, hence necessitating treatment.

Diagnosis is usually done clinically depending upon history & signs and symptoms.

Treatment for Rash on Inner Thighs

For most rashes home remedies can effectively alleviate symptoms. Drugs and others allopathic interventions are reserved for severe &/or complicated cases.

Treatment should start with immediate removal of the offending agent e.g. drug in allergic drug eruptions and advising personal and /or baby hygiene methods when needed.

Home remedies

  • Application of ice packs or even bathing the affected area with cold water – to soothe
  • Addition to bathing water, of substances like oatmeal, chamomile tea (soothe); neem & liquorice to eliminate toxins and infections.
  • Various creams and lotions e.g. – those with aloe vera, calamine; cod liver, vitamin E and Olive oil- reduce irritation and hasten healing. Relieve skin tenderness and decrease its redness.
  • Ascorbic Acid supplements should be taken for better wound healing.
  • Apple cider vinegar mixed with honey(thrice daily)- controls allergies

Medications

  • Common for all types of rash- Moisturizing ointments especially those with retinoid derivatives; Antihistamines (oral &/or topical) to reduce skin irritation especially allergy
  • For severe symptoms not responding to the above- immunosuppressant, corticosteroids and/or analgesics (oral &/or topical)
  • To treat underlying disease- Disease-specific drugs whether taken orally or for topical application like antibacterial and antifungal drugs for infections should be given according to guidelines and patient requirement.

Interventions may be needed in some cases. For example PUVA (phototherapy) for psoriatic rash, surgical removal of warts or carbuncle drainage etc.

Finally in pregnancy, Impetigo herpetiformis and Pemphigoid gestationis need to be treated aggressively with corticosteroid creams and ± antihistamines to prevent harm to the baby.

Pictures of Rash on Inner Thighs

rash on inner thighs Picture 1 – Rash on inner thighs in Female

rash on inner thighs pictures 2 Picture 2 – Rash on inner thighs from rubbing together

rash on inner thighs pictures 3 Picture 3 – Rash on inner thighs and buttocks

rash on inner thighs near groin Rash on inner thighs near groin

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