Although wetness alone has the effect of macerating the skin, softening the stratum corneum, and greatly increasing susceptibility to friction injury, urine has an additional impact on skin integrity because of its effect on skin pH. While studies show that ammonia alone is only a mild skin irritant, when urea breaks down in the presence of fecal urease it increases pH because ammonia is released, which in turn promotes the activity of fecal enzymes such as protease and lipase. These fecal enzymes increase the skin's hydration and permeability to bile salts which also act as skin irritants.

There is no detectable difference in rates of diaper rash in conventional disposable diaper wearers and reusable cloth diaper wearers. "Babies wearing superabsorbent disposable diapers with a central gelling material have fewer episodes of diaper dermatitis compared with their counterparts wearing cloth diapers. However, keep in mind that superabsorbent diapers contain dyes that were suspected to cause allergic contact dermatitis (ACD)." Whether wearing cloth or disposable diapers they should be changed frequently to prevent diaper rash, even if they don't feel wet. To reduce the incidence of diaper rash, disposable diapers have been engineered to pull moisture away from the baby's skin using synthetic non-biodegradable gel. Today, cloth diapers use newly available superabsorbent microfiber cloth placed in a pocket with a layer of light permeable material that contacts the skin. This design serves to pull moisture away from the skin in to the microfiber cloth. This technology is used in most major pocket cloth diapers brands today.

The interaction between fecal enzyme activity and IDD explains the observation that infant diet and diaper rash are linked because fecal enzymes are in turn affected by diet. Breast-fed babies, for example, have a lower incidence of diaper rash, possibly because their stools have higher pH and lower enzymatic activity. Diaper rash is also most likely to be diagnosed in infants 8–12 months old, perhaps in response to an increase in eating solid foods and dietary changes around that age that affect fecal composition. Any time an infant’s diet undergoes a significant change (i.e. from breast milk to formula or from milk to solids) there appears to be an increased likelihood of diaper rash.

The link between feces and IDD is also apparent in the observation that infants are more susceptible to developing diaper rash after treating with antibiotics, which affect the intestinal microflora. Also, there is an increased incidence of diaper rash in infants who have suffered from diarrhea in the previous 48 hours, which may be because fecal enzymes such as lipase and protease are more active in feces which have passed rapidly through the gastrointestinal tract.

With no particular affinity to any particular ethnic group, seen in all age groups and equally amongst males and females, the precise prevalence is not known.

An intertrigo usually develops from the chafing of warm, moist skin in the areas of the inner thighs and genitalia, the armpits, under the breasts, the underside of the belly, behind the ears, and the web spaces between the toes and fingers. An intertrigo usually appears red and raw-looking, and may also itch, ooze, and be sore. Intertrigos occur more often among overweight individuals, those with diabetes, those restricted to bed rest or diaper use, and those who use medical devices, like artificial limbs, that trap moisture against the skin. Also, there are several skin diseases that can cause an intertrigo to develop, such as dermatitis or inverse psoriasis.

Other rashes that occur in a widespread distribution can look like an id reaction. These include atopic dermatitis, contact dermatitis, dyshidrosis, photodermatitis, scabies and drug eruptions.

Hospital wards and, nurseries, and can be passed from person to person. Also many close contact sports. Therefore, it is advised that the patient has to try to limit as much human contact as possible to limit transmission of infection.

Bacterial intertrigo can be caused by "Streptococci" and "Corynebacterium minutissimum".

After 48 hours the disease is considered no longer contagious assuming the proper antibiotic treatments have been administered.

Erythema (redness) multiforme (EM) is usually a reaction of the skin and mucous membranes that occurs suddenly. It appears as a symmetrical rash and may include the mucous membrane lesions. This means that the body is sensitive to something that causes the skin and mucous membranes to react. The more common mild form is refer to as EM minor. It consists of a skin rash that involve no more than one mucosal surface. The sudden onset will progress rapidly as symmetrical lesions with circular color changes in some or all of the lesions. Rash will spread towards center or trunk of the body. Evenly distributed bumps on the skin become classic iris or target lesions. They have bright red borders and small white bumps in the center.

The cause of EM appears to be a highly sensitive reaction that can be triggered by a variety of causes. The causes can include bacterial, viral or chemical products, such as antibiotics – specifically penicillins or cephalosporins. This reaction is an allergic reaction and is in no way contagious.

Erythema multiforme minus is sometimes divided into papular and vesiulobullous forms.

Bullous drug reaction (also known as a "bullous drug eruption", "generalized bullous fixed drug eruption", and "multilocular bullous fixed drug eruption") most commonly refers to a drug reaction in the erythema multiforme group. These are uncommon reactions to medications, with an incidence of 0.4 to 1.2 per million person-years for toxic epidermal necrolysis and 1.2 to 6.0 per million person-years for Stevens–Johnson syndrome. The primary skin lesions are large erythemas (faintly discernible even after confluence), most often irregularly distributed and of a characteristic purplish-livid color, at times with flaccid blisters.

It is very rare and estimated to affect 1 in 100,000 per year. Because of its rarity the documentation, cases and information are sparse and not a huge amount is known for certain, meaning that EAC could actually be a set of many un-classified skin lesions. It is known to occur at all ages and all genders equally. Some articles state that women are more likely to be affected than men.

Often no specific cause for the eruptions is found. However, it is sometimes linked to underlying diseases and conditions such as:

- Food (including blue cheese or tomatoes).

- Contact Dermatitis (i.e. cleaning agents, fabric softeners, etc.)

- Fungal, Bacterial and Viral infections such as sinusitis, tuberculosis, candidiasis or tinea.

- Drugs including finasteride, etizolam (and benzodiazepines), chloroquine, hydroxychloroquine, oestrogen, penicillin and amitriptyline.

- Cancer (especially the type known as erythema gyratum perstans, in which there are concentric and whirling rings).

- Primary biliary cirrhosis.

- Graves disease.

- Appendicitis.

- Lupus

- Pregnancy (EAC usually disappears/stops soon after delivery of baby).

- Hormone (Contraceptive Pill, Stress, Hormone Drugs)

- Lyme Disease

Many suspected aetiologic factors have been reported to cause EM.

- Infections: Bacterial (including Bacillus Calmette-Guérin (BCG) vaccination, haemolytic "Streptococci", legionellosis, leprosy, "Neisseria meningitidis, Mycobacterium, "Pneumococcus, "Salmonella" species, "Staphylococcus" species, "Mycoplasma pneumoniae), "Chlamydial.

- Fungal (Coccidioides immitis)

- Parasitic ("Trichomonas" species, "Toxoplasma gondii), "

- Viral (especially Herpes simplex)

- Drug reactions, most commonly to: antibiotics (including, sulphonamides, penicillin), anticonvulsants (phenytoin, barbiturates), aspirin, antituberculoids, and allopurinol and many others.

- Physical factors: radiotherapy, cold, sunlight

- Others: collagen diseases, vasculitides, non-Hodgkin lymphoma, leukaemia, multiple myeloma, myeloid metaplasia, polycythemia

EM minor is regarded as being triggered by HSV in almost all cases. A herpetic aetiology also accounts for 55% of cases of EM major. Among the other infections, "Mycoplasma" infection appears to be a common cause.

Herpes simplex virus suppression and even prophylaxis (with acyclovir) has been shown to prevent recurrent erythema multiforme eruption.

Erythema ab igne was once commonly seen in the elderly who stood or sat closely to open fires or electric heaters; however, erythema ab igne has been reported in both young and elderly individuals. Women have a higher incidence of erythema ab igne than men. Although wide use of central heating has reduced the overall incidence of erythema ab igne, it is still sometimes found in people exposed to heat from other sources such as heating pads, space heaters, hot water bottles, and electronic devices.

Dermatophytids are fungus-free disseminated skin lesions resulting from induced sensitization in patients with ringworm infections.

The most common dermatophytid is an inflammation in the hands resulting from a fungus infection of the feet. Dermatophytids normally disappear when the primary ringworm infection is treated.

Dermatophytids may resemble erythema nodosum.

The cause of erythema toxicum is thought to be an activation of the immune system. Some neonates are more sensitive than others and develop erythematous spots all over the body. Another theory is hypersensitivity to detergents in bedsheets and clothing is sometimes suspected, but the connection remains unproven.

It is thought to be a benign condition that causes no discomfort to the infant. The rash will generally disappear spontaneously in about 2 weeks.

Different types of heat sources can cause this condition such as:

- Repeated application of hot water bottles, heating blankets or heat pads to treat chronic pain—e.g., chronic backache.

- Repeated exposure to heated car seats, space heaters, or fireplaces. Repeated or prolonged exposure to a heater is a common cause of this condition in elderly individuals.

- Occupational hazards of silversmiths and jewellers (face exposed to heat), bakers and chefs (arms)

- Resting a laptop computer on the thigh (laptop computer-induced erythema ab igne). In a 2012 review, Riahi and Cohen describe the characteristics of laptop computer-induced erythema ab igne. Temperatures between 43-47 °C can cause this skin condition; modern laptops can generate temperatures in this range. Indeed, laptops with powerful processors can reach temperatures of 50 °C and be associated with burns. Positioning of the laptop on the thighs can allow for direct exposure to the heating elements of the laptop, which include the central processing unit (CPU) and the graphics processing unit (GPU). At least 15 cases have been reported by 2012 with the condition usually affecting the left anterior thigh. In these reports, 9 of the 15 patients were women (60%) with an average age of 25 years at diagnosis.

- In Kashmir, due to the use of a kanger which also causes kangri cancer

- It is a classic finding in chronic pancreatitis and may also be seen in people with hypothyroidism or lymphoedema

Because the eruption is transient and self-limiting, no treatment is indicated.

Erythema multiforme is frequently self-limiting and requires no treatment. The appropriateness of glucocorticoid therapy can be uncertain, because it is difficult to determine if the course will be a resolving one.

Staphylococcal scalded skin syndrome, (SSSS), also known as Pemphigus neonatorum or Ritter's disease, or Localized bullous impetigo is a dermatological condition caused by "Staphylococcus aureus".

The prognosis of SSSS in children is excellent, with complete resolution within 10 days of treatment, and without significant scarring. However, SSSS must be differentiated carefully from toxic epidermal necrolysis, which carries a poor prognosis. The prognosis in adults is generally much worse, and depends upon various factors such as time to treatment, host immunity, and comorbidities.

Psoriasis has been associated with obesity and several other cardiovascular and metabolic disturbances. The incidence of diabetes is 27% higher in people affected by psoriasis than in those without the condition. Severe psoriasis may be even more strongly associated with the development of diabetes than mild psoriasis. Younger people with psoriasis may also be at increased risk for developing diabetes. Individuals with psoriasis or psoriatic arthritis have a slightly higher risk of heart disease and heart attacks when compared to the general population. Cardiovascular disease risk appeared to be correlated with the severity of psoriasis and its duration. There is no strong evidence to suggest that psoriasis is associated with an increased risk of death from cardiovascular events. Methotrexate may provide a degree of protection for the heart.

The odds of having hypertension are 1.58 times higher in people with psoriasis than those without the condition; these odds are even higher with severe cases of psoriasis. A similar association was noted in people who have psoriatic arthritis—the odds of having hypertension were found to be 2.07 times greater when compared to odds of the general population. The link between psoriasis and hypertension is not currently understood. Mechanisms hypothesized to be involved in this relationship include the following: dysregulation of the renin-angiotensin system, elevated levels of endothelin 1 in the blood, and increased oxidative stress. The incidence of the heart rhythm abnormality atrial fibrillation is 1.31 times higher in people with mild psoriasis and 1.63 times higher in people with severe psoriasis. There may be a slightly increased risk of stroke associated with psoriasis, especially in severe cases. Treating high levels of cholesterol with statins has been associated with decreased psoriasis severity, as measured by PASI score, and has also been associated with improvements in other cardiovascular disease risk factors such as markers of inflammation. These cardioprotective effects are attributed to ability of statins to improve blood lipid profile and because of their anti-inflammatory effects. Statin use in those with psoriasis and hyperlipidemia was associated with decreased levels of high-sensitivity C-reactive protein and TNFα as well as decreased activity of the immune protein LFA-1. Compared to individuals without psoriasis, those affected by psoriasis are more likely to satisfy the criteria for metabolic syndrome.

Riehl melanosis is a form of contact dermatitis, beginning with pruritus, erythema, and pigmentation that gradually spreads which, after reaching a certain extent, becomes stationary. The pathogenesis of Riehl melanosis is believed to be sun exposure following the use of some perfumes or creams (a photocontact dermatitis).

The rates of Crohn's disease and ulcerative colitis are increased when compared with the general population, by a factor of 3.8 and 7.5 respectively. People with psoriasis also have a higher risk of celiac disease. Few studies have evaluated the association of multiple sclerosis with psoriasis, and the relationship has been questioned. Psoriasis has been associated with a 16% increase in overall relative risk for non-skin cancer. People with psoriasis have a 52% increased risk cancers of the lung and bronchus, a 205% increase in the risk of developing cancers of the upper gastrointestinal tract, a 31% increase in the risk of developing cancers of the urinary tract, a 90% increase in the risk of developing liver cancer, and a 46% increase in the risk of developing pancreatic cancer. The risk for development of non-melanoma skin cancers is also increased. Psoriasis increases the risk of developing squamous cell carcinoma of the skin by 431% and increases the risk of basal cell carcinoma by 100%. There is no increased risk of melanoma associated with psoriasis.

Some sources distinguish between the following:

- "Erythema marginatum rheumaticum"

- "Erythema marginatum perstans"