This rare skin condition can cause painful skin bumps or lesions. While there’s a lot that’s still unknown about what causes Sweet syndrome, many factors may play a role in its development.

Sweet syndrome is a rare skin condition. It’s a type of neutrophilic dermatosis, which is a general term for a group of skin disorders that occur when there’s a buildup of neutrophils. Neutrophils are a specific type of infection-fighting white blood cell in the skin.

Sweet syndrome may also be referred to as acute febrile neutrophilic dermatosis. It was first described by Dr. Robert Douglas Sweet in 1964.

There are three main types of Sweet syndrome:

  • classic or idiopathic (no identified cause)
  • malignancy-associated (related to cancer)
  • drug-induced (triggered by a drug)

Classic Sweet syndrome is the most common type. This form of Sweet syndrome often develops after an upper respiratory infection or gastrointestinal (GI) infection.

The primary symptom of Sweet syndrome is the rapid onset of tender or painful bumps or lesions on the skin. While these lesions can appear anywhere on the body, they commonly affect the:

  • arms
  • face
  • neck
  • chest
  • back
  • legs

It’s possible to have just one skin bump or several lesions that connect to each other. They often have a clear blister and sometimes have an annular or target-like appearance.

People with Sweet syndrome generally feel very ill and may experience additional symptoms, including:

Other areas of the body can be affected by Sweet syndrome, including the:

  • bones
  • central nervous system
  • ears
  • eyes
  • kidneys
  • intestines
  • liver
  • heart
  • lungs
  • mouth
  • muscles
  • spleen

Eye complications such as conjunctivitis and episclera are common with classic Sweet syndrome.

Mouth sores are more likely to occur in those who have hematologic disorders, such as blood cancer.

The exact cause of Sweet syndrome is unknown.

It’s thought that various contributing factors may play a role in the development of the condition, either on their own or in part, such as:

  • an existing autoimmune or inflammatory condition such as Crohn’s, ulcerative colitis, rheumatoid arthritis, or lupus
  • infections of the upper respiratory tract
  • infections of the GI tract
  • blood cancer such as leukemia or lymphoma
  • other forms of cancer, such as bowel cancer or breast cancer
  • sun exposure
  • use of certain medications
  • certain vaccinations
  • pregnancy

More research is needed to help understand what may trigger or cause the development of Sweet syndrome.

Sweet syndrome is not a common condition, but a few factors may increase your risk:

  • being a woman
  • being between the ages of 30 and 50
  • having recently recovered from an infection of the upper respiratory tract or GI tract
  • having cancer such as leukemia, lymphoma, or breast cancer
  • having Crohn’s disease or ulcerative colitis
  • being pregnant

In most cases, Sweet syndrome is diagnosed based on the following:

  • a detailed medical history
  • physical exam
  • blood work
  • a skin biopsy

The major diagnositic criteria for classic Sweet syndrome includes an abrupt onset of tender or painful bumps or lesions on the skin, plus biopsy results that confirm the presence of inflammatory neutrophils.

Minor diagnositic criteria also include:

Sweet syndrome is rare and may not be quickly diagnosed. Your doctor may send you to a dermatologist for diagnosis and treatment.

If organs other than skin are suspected to be involved, your doctor or dermatologist may also order specialized tests.

In some cases, the skin lesions related to Sweet syndrome will heal on their own. However, they may take weeks or months to resolve.

For those who seek treatment, corticosteroids, such as prednisone, are the most common option for Sweet syndrome. Corticosteroids can be applied topically to the skin or injected directly into the affected lesion.

If steroids don’t work, other treatment options include:

Drug-induced Sweet syndrome often goes away once you stop taking the medication that brought on these symptoms. If you have an underlying condition such as Crohn’s disease or cancer, that treatment should help resolve the symptoms of Sweet syndrome.

Your doctor will determine which form of medication and treatment is right for you. For some people with Sweet syndrome, skin lesions may recur, even with treatment.

Home care

If you have lesions on your skin, you also need to practice proper wound care to prevent infection. Follow any skin care instructions or medication schedule prescribed by your doctor.

Some research suggests protecting your skin from prolonged sun exposure is a good way prevent Sweet syndrome and avoid a recurrence of symptoms.

According to the American Academy of Dermatology, good sun protection practices include the following:

  • Use sunscreen with a sun protection factor (SPF) of at least 30.
  • Wear protective clothing, including items such as wide-brimmed hats, long-sleeved shirts, and sunglasses.
  • Avoid scheduling outdoor activities between 10 a.m. and 2 p.m., when the sun is the strongest.
  • Seek shady areas when you’re spending time outside.

Left untreated, Sweet syndrome can take anywhere from weeks or months to resolve on its own. With medication, Sweet syndrome is likely to clear up faster than if it’s left untreated.

The skin lesions of Sweet syndrome usually resolve without leaving a scar.

Practicing proper wound care and protecting skin from the sun can also help prevent infection and recurrence.

If you experience a sudden rash that spreads, you should contact your doctor or dermatologist as soon as possible. Proper diagnosis and treatment can help you manage symptoms and prevent the condition from recurring.