Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) that affects the large intestine, but it can also cause skin issues. These can include painful rashes.

Skin issues affect about 15 percent of all people with different types of IBD.

Some of the skin rashes may come as a result of inflammation within your body. Other skin issues linked to UC may be caused by the medications you take to treat UC.

A number of different types of skin issues can be caused by UC, especially during flare-ups of the condition.

Pictures of UC skin rashes

10 skin issues associated with UC

1. Erythema nodosum

Erythema nodosum is the most common skin issue for people with IBD. Erythema nodosum are tender red nodules that usually appear on the skin of your legs or arms. The nodules may also look like a bruise on your skin.

Erythema nodosum affects anywhere from 3 to 10 percent of people with UC. It’s seen more in women than men.

This condition tends to coincide with flare-ups, sometimes occurring just before a flare starts. Once your UC is under control again, the erythema nodosum will likely go away.

2. Pyoderma gangrenosum

Pyoderma gangrenosum is the second most common skin issue in people with IBD. One large study of 950 adults with IBD found that pyoderma gangrenosum affected 2 percent of people with UC.

Pyoderma gangrenosum starts as a cluster of small blisters that can spread and combine to create deep ulcers. It’s usually seen on your shins and ankles, but it may also appear on your arms. It can be very painful and cause scarring. The ulcers could become infected if they’re not kept clean.

Pyoderma gangrenosum is thought to be caused by immune system disorders, which may also contribute to UC. Treatment involves high doses of corticosteroids and drugs that suppress your immune system. If the wounds are severe, your doctor may also prescribe pain medication for you to take.

3. Sweet’s syndrome

Sweet’s syndrome is a rare skin condition characterized by painful skin lesions. These lesions start as small, tender red or purple bumps that spread into painful clusters. They’re usually found on your face, neck, or upper limbs. Sweet’s syndrome is linked to active flare-ups of UC.

Sweet’s syndrome is often treated with corticosteroids in either pill or injection form. The lesions may go away on their own, but recurrence is common, and they can result in scars.

4. Bowel-associated dermatosis-arthritis syndrome

Bowel-associated dermatosis-arthritis syndrome (BADAS) is also known as bowel bypass syndrome or blind loop syndrome. People with the following are at risk:

  • a recent intestinal
  • diverticulitis
  • appendicitis
  • IBD

Doctors think that it may be caused by overgrown bacteria, leading to inflammation.

BADAS causes small, painful bumps that may form into pustules over the course of one to two days. These lesions are usually found on your upper chest and arms. It can also cause lesions that look like bruises on your legs, similar to erythema nodosum.

The lesions usually go away on their own but may come back if your UC flares up again. Treatment may include corticosteroids and antibiotics.

5. Psoriasis

Psoriasis, an immune disorder, is also associated with IBD. In a study from 1982, 5.7 percent of people with UC also had psoriasis.

Psoriasis results in a buildup of skin cells that form white or silver-looking scales in raised, red patches of skin. Treatment may include topical corticosteroids or retinoids.

6. Vitiligo

Vitiligo occurs more often in people with UC and Crohn’s than in the overall population. In vitiligo, the cells that are responsible for producing the pigment of your skin are destroyed, leading to white patches of skin. These white patches of skin can develop anywhere on your body.

Researchers think that vitiligo is also an immune disorder. An estimated 20 percent of people with vitiligo have another immune disorder as well, such as UC.

Treatment can include topical corticosteroids or a combination pill and light treatment known as psoralen and ultraviolet A (PUVA) therapy.

Learn more: What does vitiligo look like? »

7. Pyodermatitis-pyostomatitis vegetans

Pyodermatitis vegetans is a rash with red pustules that can rupture and form raised scaly patches of skin known as plaques. It’s usually found in the skin folds of your armpit or groin. It’s linked to a similar skin condition known as pyostomatitis vegetans, in which pustules form in your mouth. The two conditions are collectively known as pyodermatitis-pyostomatitis vegetans (PPV).

PPV is so closely linked to UC that some people are only diagnosed with UC after one or both forms of PPV develop. The pustules usually appear after UC has been active for several years.

8. Leukocytoclastic vasculitis

Leukocytoclastic vasculitis is also known as hypersensitivity vasculitis. In leukocytoclastic vasculitis, inflammation causes small blood vessels to burst and blood to pool under your skin. This leads to purple-colored spots known as purpura. The spots can be small or large patches and are usually found on your ankles or legs.

In most cases of leukocytoclastic vasculitis, the skin lesions go away once the underlying UC is treated.

9. Acne

Ulcerative colitis is also linked to cystic acne in some people. Cystic acne is a painful type of acne that develops under your skin. Cystic acne can be treated with topical prescriptions like retinol or benzoyl peroxide.

If you have cystic acne and either have UC or are at high risk of developing it, you shouldn’t use the prescription drug Accutane. Accutane has been linked to UC and other IBDs.

Read more: Acne treatment types and side effects »

10. Hives

Hives are red and often itchy skin rashes that can appear on any part of your body. UC is linked to cases of chronic hives. They may occur as a reaction to medications you take to manage your UC.

If you start a new medication and experience persistent hives, contact your doctor about alternatives.

What to do during a flare-up

Most skin issues associated with UC are best treated by managing the UC as much as possible, as many of these rashes can coincide with UC flare-ups. Others may be the first sign of UC in someone who hasn’t been diagnosed yet.

Corticosteroids can help with the inflammation that often causes the skin issues associated with UC. Eating a well-balanced diet can help promote overall health and may aid in preventing skin issues.

When you do experience a flare-up of UC skin rash, there are several things you can try:

  • Keep
    the lesion clean to prevent infections.
  • See
    your doctor for prescription antibiotic ointment or pain medication if needed.
  • Keep
    lesions covered with a moist bandage to promote healing.