Rash Behind Knees

A rash occurring behind the knees is not a common condition. On most occasions, the reason for the rash is because of contact with an irritant of some kind. The most common reasons for rashes occurring on the body are from an allergic reaction because of skin contact or an allergic reaction to medication.


A rash occurring behind the knees could happen for any number of reasons. It’s understandable to become nervous about the cause of it and worry if the symptoms are serious. A person could believe they have contracted a rare skin disease or they fear they are beginning to see the manifestation of early stages of skin cancer. In many cases, the skin rash is caused by atopic dermatitis. Other causes, some serious, will be discussed later in the article.


The causes of rashes behind the knees are wide-ranging. The first cause could be dermatitis herpetiformis. This is a rash that happens either on your back, elbows, knees, scalp or your butt. An allergic reaction to gluten is the most likely cause of this rash which may be indicative of celiac disease. Celiac disease is an allergic reaction to gluten. Other names for celiac disease are:

  • Gluten-sensitive enteropathy
  • Nontropical sprue
  • Sprue

Gluten is contained in foods that are made with barley, rye, wheat as well as triticale. Oats contain gluten too if they are produced in a plant that handles other grains. Gluten is even in certain kinds of medicines, lipsticks and vitamins. Some symptoms of celiac disease include:

The symptoms as seen in children:

  • Weight loss
  • Irritability
  • Vomiting
  • Feeling tired
  • Bloating
  • Pain in the abdomen
  • Constipation or diarrhea
  • Pale, unpleasant smelling stool

The symptoms as seen in adults:

  • Brittle and weak bones
  • Feeling tired
  • Seizures
  • Pain in joints
  • Stiffness
  • Anemia resulting from iron deficiency
  • Disorders in the skin
  • Tingling or numbness in extremities
  • Tooth discoloration
  • Loss of tooth enamel
  • Miscarriage and infertility
  • Sores in the mouth

Other possible causes of behind the knee rashes are:

  • Stasis dermatitis
  • Seborrheic dermatitis
  • HIV infection
  • Dry skin
  • Melanoma
  • Pyoderma gangrenosum
  • Psoriasis
  • Syphilis

More causes of rash behind knees could include any of the following:

  • Flea bites
  • Fifth disease
  • Bites or stings from an insect
  • Shingles
  • Impetigo
  • Scabies
  • Hay fever
  • Eczema
  • Scarlet fever
  • Rheumatic fever
  • Mononucleosis
  • Measles
  • Ringworm
  • Yeast infection
  • German measles
  • Stasis dermatitis
  • Lyme disease
  • West Nile virus
  • Cellulitis
  • MRSA
  • Toxic shock syndrome
  • Lupus
  • Acrodermatitis
  • Hookworm
  • Typhoid
  • Dengue fever
  • SARS
  • Ebola


The symptoms of a rash are typically red, irritated skin, slight discoloration, itchiness, rough, scaly feeling skin and bleeding if scratched. More serious symptoms require immediate attention from your doctor. These symptoms are:

  • Sore throat
  • Joint pain
  • A very recent bite from an animal or insect
  • Skin is tender near the rash
  • Pus is prevalent near rash
  • Skin changes color
  • High temperature from fever
  • Sense of confusion
  • Feelings of dizziness
  • Facial swelling
  • Extremity swelling
  • Intense pain in our head or neck
  • Excessive vomiting
  • Excessive diarrhea
  • Difficulty breathing

How to treat rashes behind knees:

The best options for treatment always come from your doctor’s care. Your doctor will evaluate you and determine the best plan of care for your individual needs. There is not one way to treat a rash as there are many causes. Depending on what kind of rash had, will determine what your treatment will be.

Diet can be a contributing factor for the occurrence of rashes. One of the most effective forms of treatment is a diet that is free of gluten. You should avoid any foods, drinks, or medications that contain any of the following:

  • Barley
  • Oats
  • Rye
  • Wheat

By reducing your intake of gluten, it will help in reducing the amount of medication you are required to take.

The common treatments for rashes like atopic eczema are medications. Creams and ointments purchased at your local pharmacy are an option. These creams have to contain steroid hydrocortisone. Some creams that contain it are: Dermarest Eczema, Cortizone-10, Cort-Aid and Neosporin Eczema. If you are dealing with mid-level eczema, a topical immunomodulator should be able to help you. These work because they modify your body’s response to allergens and stop flare ups when you come into contact with an allergen. Antibiotics and antihistamines have proven successful in stopping the itching symptoms.

Another available treatment option for you is phototherapy. Phototherapy involves doctors using ultraviolet light waves to treat people with cases of severe eczema. The two kinds of ultraviolet light used are ultraviolet A (UVA) or ultraviolet B (UVB). However, there are some health concerns associated with phototherapy. Patients treated with this method may experience, itchy skin, dry skin, freckles appearing and your skin may age at a faster rate.

Frequently asked questions:

Can rash behind knees be prevented?

  • Unfortunately, no. Similar to the common cold, you don’t know you have had bacteria enter your body until the cold starts. Your skin’s reaction to an irritant lets you know that is an irritant. What can be done is limiting the timeline the rash has on your body. This is done by:
  • Lowering stress levels
  • Staying away from materials that scratch the skin like wool
  • Avoiding harsh chemicals in some soaps, solvents and detergents
  • Keep the skin moisturized often
  • Stay away from sudden changes in humidity and temperature
  • Stay cool to avoid our skin overheating

How long will the rash last?

The timeline of the rash depends on the severity of your symptoms. In many cases, an ointment will serve as sufficient treatment, but other cases require medication and if the rash is a symptom of cancer, surgery may be required to remove the cancer in your body.

How will I know if this is a common or serious rash?

This question can be best answered by your doctor. While you can do research online, this can cause you added stress if you self-diagnose and can make the rash worse. Another conclusion people tend to jump to is self-treatment. This is highly unrecommended because there are specific tests done to determine what treatment is right for you. Contact your doctor at the first sign of a rash to determine the best course of action.

Last Reviewed:
June 23, 2018
Last Updated:
June 21, 2018