Pathergy and skin sensitivity in Sweet’s syndrome

Updated on 3/02/2017.

Some people with Sweet’s syndrome seem to be very sensitive to skin damage – why is this?

We are not entirely sure why some people with Sweet’s syndrome are more sensitive to skin damage than others, but we do know that it is part of a pathergy response. This is an unusual response that is sometimes incorrectly referred to as Koebner phenomenon (isomorphic response), but even though they are similar, they are not exactly the same thing.

What is Koebner phenomenon?

The Koebner phenomenon is named after the German dermatologist Heinrich Koebner (1838–1904) who first recognised it in psoriasis patients. It is a phenomenon that causes skin lesions to appear at the site of a skin injury in otherwise healthy skin. In patients demonstrating a true Koebner response, this phenomenon can be confirmed by experimentally reproducing lesions with different methods of injury. These lesions will then normally appear in a linear shape (in lines).

In which conditions can Koebner phenomenon be seen?

Koebner phenomenon is most commonly seen in those with psoriasis, vitiligo and lichen planus, but can occasionally be seen in other conditions too.

Can it occur for other reasons?

Yes. Koebner phenomenon can occur for lots of other reasons, including overexposure to sunlight, phototherapy (light treatment), taking medications that suppress or ‘dampen down’ the immune system, and withdrawal from methotrexate therapy – a medication that is used to treat cancer, autoimmune conditions, and occasionally, Sweet’s syndrome.

What causes Koebner phenomenon?

We are not entirely sure what causes Koebner phenomenon. Current theories suggest that it is a phenomenon that requires both the outer layer (epidermis) and underlying or inner layer of the skin (dermis) to be injured at the same site. The production of inflammatory substances and neuropeptides (small protein-like molecules used by nerve cells to communicate with each other) have also been suggested as an initial step in a process that eventually leads to Koebner phenomenon. Chemical messengers such as nerve growth factor (NGF) may play a role, but this is still being investigated.

What is pathergy?

Pathergy, sometimes referred to as skin hypersensitivity, is an exaggerated skin injury that occurs as a result of minor skin damage or irritation. It typically occurs after minor skin damage such as a bump or bruise, or needle stick injury, e.g. injury caused by an injection or having blood taken. The injury then leads to the development of skin lesions, i.e. papules (red bumps) or pustules. However, a more severe injury, e.g. a surgical procedure, can sometimes result in ulceration.

In which conditions can pathergy be seen?

Pathergy is most commonly seen in those with the neutrophilic dermatosis, Behcet’s syndrome. However, it can sometimes be seen in patients with other forms of neutrophilic dermatosis, e.g. Sweet’s syndrome and pyoderma gangrenosum.

What causes pathergy?

Unfortunately, the actual cause of pathergy still remains unknown.

Sweet’s syndrome and pathergy.

How many people with Sweet’s syndrome demonstrate pathergy?

In literature, pathergy is rarely reported in those with Sweet’s syndrome, but it is known to occur in 8% of patients (Ginarte and Toribio, 2011). We still do not know why it is a problem for some people with Sweet’s syndrome but not others, and due to under-reporting may be more common than first thought.

What kind of injury can cause skin lesions to develop in people with Sweet’s syndrome?

In those with Sweet’s syndrome who demonstrate pathergy, skin lesions (Sweet’s lesions) have been reported to have developed as a result of:

  • Something that causes irritation when it comes into contact with the skin, scratches, skin damage caused by a biopsy, injection or having blood taken, insect bites, radiotherapy, and in areas exposed to the sun (Cohen, 2007; Verma et al, 2014).
  • Wound debridement (removal of affected tissue), particularly surgical wound debridement (surgical removal of affected tissue) (Cohen, 2007; Kroshinsky et al, 2012; Leighton and Amirfeyz, 2015; Otero et al , 2017; Shugarman et al, 2011).
  • Oral pathergy. In 2016, the first case of oral pathergy affecting the mouth, tongue and pharynx was reported (Klimpl et al, 2016).

What can you do to help yourself?

If you have problems with pathergy take care to avoid:

  • Sunburn – be careful about overexposure to both sunlight and ultraviolet (UV) light.
  • Contact with irritants.
  • Scratching.
  • Ideally, surgical procedures should only be performed when the Sweet’s syndrome has settled down or is in remission. Wound debridement of a Sweet’s lesion should be avoided.

You can also:

  • Keep your skin well moisturised to help prevent areas of dryness and irritation. Choose products that are suitable for sensitive skin.
  • Avoid harsh cleansing solutions, e.g. strong antiseptic or alcohol-based solutions, and clean your lesions with water, saline or a very mild cleansing solution.
  • Try to avoid ‘treating’ lesions with essential oils or use with caution. There is no medical evidence to show that essential oils are a safe or effective treatment, and may cause irritation.
  • Be aware of the fact that even natural herbal extracts and creams can potentially irritate the skin.
  • Do not apply red root (blood root, bloodwort) to your skin lesions. This is a debriding agent (removes tissue) that is sometimes advocated as a treatment for Sweet’s syndrome by some alternative therapists. There is no medical evidence to show that this is a safe or effective treatment, and may cause new lesions to develop.
  • Avoid or be careful when using or removing anything adhesive, e.g. plasters, tapes, dressings, or temporary tattoos.
  • Be careful of anything that rubs or chafes the skin.
  • Avoid or be careful when using cosmetic or beauty treatments, or body art that could irritate or damage the skin, e.g. facial peels, rough exfoliators, leg waxing, tweezing, henna tattoos, tattoos, or piercings.

A warning about skin prick tests for food allergy and intolerance.

  • Some Sweet’s syndrome patients are being told by alternative therapists that Sweet’s syndrome is directly caused by food allergy or intolerance, and that they need a skin prick test. This is completely untrue, and there is no evidence to support these claims.

  • Skin prick ALLERGY tests may be unreliable in some people with Sweet’s syndrome. This is because any reaction that does occur may be pathergy rather than genuine allergic reaction. However, if the skin prick allergy test is carried out in the correct way, that can help to rule out other kinds of reaction.

  • If a patient has a skin prick allergy test and the result is positive, then wheals or hives develop in the area where the allergen, i.e. the substance that someone is allergic to, has been applied. These wheals and hives can sometimes be mistaken for Sweet’s lesions or vice versa.

  • Skin prick tests CANNOT be used to diagnose a food INTOLERANCE. These tests are a SCAM.


Cohen, P. (2007) Sweet’s syndrome – a comprehensive review of an acute febrile neutrophilic dermatosis. Orphanet, Jul 26;2:34 (online).

Ginarte, M. and Toribio, J. (2011) Sweet’s Syndrome. IntechOpen Online.

Klimpl, D., Manser. T. and Flemmer, M. (2016) Oral Pathergy in Sweet’s Syndrome Following Food Bolus Injury, Case Reports in Clinical Medicine, Apr; 5(4): 134-139 (Scientific Research – Online). Download as free PDF.

Kroshinsky, D., Alloo, A., Rothschild, B., Cummins, J., Tan, J., Montecino, R., Hoang, M., Duncan, L., Mihm, M. and Sepehr, A. (2012) Necrotizing Sweet syndrome: a new variant of neutrophilic dermatosis mimicking necrotizing fasciitis. Journal of the American Academy of Dermatology, Nov;67(5):945-54 (PubMed).

Leighton, P. and Amirfeyz, R. (2015) Sweet syndrome: a lesson in the management of the cutaneous lesions of malignancy. Journal of Surgical Case Reports, Feb 11th (online).

Otero, T., Barber, S., Yeh, D. and Quraishi, S. (2017) Necrotizing Soft Tissue Infection or Sweet Syndrome: Surgery Versus No Surgery? A Case Report. A&A Case Reports. Feb 1 (PubMed).

Shugarman, I., Schmit, J., Sbicca, J. and Wirk, B. (2011) Easily Missed Extracutaneous Manifestation of Malignancy-Associated Sweet’s Syndrome: Systemic Inflammatory Response Syndrome. American Society of Clinical Oncology, Aug 20; 29(24) (online).

Verma, R., Vasudevan, B. and Mitra, D. (2014) Unusual presentation of idiopathic sweet’s syndrome in a photodistributed pattern. Indian Journal of Dermatology; 59(2): 186-189 (online).

Further information.

Oakley, A. (2011) Pathergy. DermNet NZ (online).

Oakley, A. (2015) Sweet disease/ DermNet NZ (online). Published in 1998, and updated Sept. 2015.

Qiao, J., Wang, Y., Bai, J., Wu, Y. and Fang, H. (2015) Concurrence of Sweet’s Syndrome, Pathergy Phenomenon and Erythema Nodosum-like Lesions. Anais Brasileiros de Dermatologia, Mar-Apr;90(2):237-9 (online).

© 2012-2017 Sweet’s Syndrome UK


4 thoughts on “Pathergy and skin sensitivity in Sweet’s syndrome

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s