What is Dermatitis?

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  • Originally Written By: Brendan McGuigan
  • Revised By: Emma Lloyd
  • Edited By: Andrew Jones
  • Last Modified Date: 17 January 2019
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Dermatitis is a catch-all term for a group of skin conditions that cause a rash. These rashes are typically, but not always, the result of an allergic reaction. Types of dermatitis include eczema and dandruff, as well as those caused by allergies. Appropriate treatment depends on the precise cause of the condition, but often includes either an oral or a topical medication. In most cases, avoiding triggers once they are identified will help the rash clear up over time.

Symptoms depend on a number of factors, including the location, severity, and duration of the reaction. The most common are an itchy rash and reddened skin, although dry flaky skin, blisters, scaly skin, and crusty lesions may also occur. The rash might have sharply-defined borders, or it might gradually fade into the surrounding skin tone, depending on the cause.


Types of Dermatitis

Contact Allergies

One of the most common types of rash is allergic contact dermatitis, which is caused by the skin being exposed to an allergen. Common allergens include certain plants, perfume and lotion fragrances, and fabric treatments and dyes. An allergic reaction can be screened for with a patch test, where a small amount of the relevant substance is rubbed on an area of exposed skin and watched for a reaction. One widely-used patch test is the True Test, which screens more than 30 distinct allergens, including various types of mold and pollen. Reactions can develop anywhere on the body that has been exposed to the allergen.


Seborrhoeic dermatitis, another common condition, is usually referred to as dandruff — or cradle cap when it occurs in infants. It most often develops on the scalp and parts of the face but can sometimes appear on the groin or chest. Dandruff is, in part, the result of the skin reacting to one of a family of yeasts called Malassezia, combined with excess production of skin oils. In most cases, it is easily treated with an antifungal agent, such as an over-the-counter anti-dandruff shampoo.


The signs and symptoms of eczema can resemble those of a contact allergy, but they stem from different causes. Although many people with eczema are also affected by seasonal allergies or asthma, this condition is caused by skin hypersensitivity rather than by an allergic reaction. A hypersensitivity reaction is one in which the immune system reacts strongly but non-specifically to a wide variety of substances, causing skin redness and irritation, and often blisters. Eczema is a chronic condition, and can be worsened by exposure to rough fabrics, chemicals, cold or dry air, sudden temperature changes, and other irritants. Stress can also cause a flare-up of symptoms.


This term refers to skin irritation that is triggered by a skin infection, but is not directly caused by it. Often, the cause is a yeast or fungal infection. For example, sometimes a primary infection with Tinea pedis, the fungus which causes athlete’s foot, can cause a secondary rash to develop elsewhere on the body. When they occur, these secondary rashes tend to appear between one and three weeks after the original infection and typically present with more severe symptoms.

Chemical Irritation

Dermatitis can be caused by exposure to a variety of chemical irritants, including acids, bases, and solvents. Strong chemicals can rapidly cause dangerous burns, but diluted ones often lead to irritation. Many people notice a rash develop if they spend extensive time in a chlorine-loaded swimming pool, for example, or if they are using heavy-duty cleaners without sufficient skin protection. Most cleaning chemicals, as well as chemicals used in metalworking, painting, and wood treatment, can cause this type of skin condition, which is why rubber gloves and other protective garments are generally recommended.

Treatment and Prevention

The root cause of the various types of dermatitis is an immune reaction that draws immune cells and molecules to the contact location. The release of immune chemicals called histamines is largely responsible for the characteristic itchiness and redness. Most treatments are therefore aimed at controlling the immune response to the triggering agent.

Treatments may vary, but some are commonly used for a range of rashes. For mild cases, an antihistamine medication is usually enough to allow the itching to subside until the rash itself heals. For more severe or chronic rashes, a medical professional might prescribe a topical steroid; however, because steroids are a broad-spectrum immune suppressant, these medications are for short-term use only. Many people find they are able to reduce or eliminate contact with the irritants that caused the rash, preventing further problems. In some cases, such as with eczema, exposure cannot be completely controlled, and long-term or even lifelong monitoring and treatment is necessary.


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Post 3

For Halloween I put a load of sparkles on my chest and shoulders, then the next day I got a weird hard bump on my chest which hurt and I thought it was a pimple so I tried to pop it so it wouldn't hurt. Later that night, it got all inflamed and turned into a rash. Does this sound like an allergic reaction?

Post 2

@ valleyFiah- Your skin problems could be one of many things. The most common causes of skin problems are the water a person bathes in, a person’s diet, or a complication of diabetes. If you think it is the water, try adding a filtering showerhead to your showers. Good ones cost about $100, and you should change filters every three to six months (about $20 a pop). Most municipal water is filled with chlorine and chloramines to kill pathogens and bacteria. Municipal water also has other VOCs and heavy metals that can irritate sensitive skin.

Diabetics are also at higher risk for skin dermatitis. Bacterial infections, fungal infections, and diabetic dermopathy are common ailments for those suffering from diabetes. Properly controlling blood sugar, regular exercise, and a healthy diet can help to reduce the risk for many diabetic skin disorders.

Post 1

I think I might have chronic dermatitis on my elbow. I am not sure what causes the rash, but it is slightly scaly, red, and itchy. What can I do to get rid of this rash? I have tried natural remedies, but I have not gone to the doctor yet. The only time it went away was when I vacationed at my sister’s house. She lives in another state, so this makes me think that the water in my shower has something to do with it. Does anyone have any ideas?

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