Pathergy and skin sensitivity in Sweet’s syndrome

Updated on 8/04/2018.

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

Doctors and researchers don’t know why some people with Sweet’s syndrome are more sensitive to skin damage than others, but we do know that it can be a pathergy response. This is similar to another kind of response called Koebner phenomenon or isomorphic response.

What is Koebner phenomenon or isomorphic response?

The Koebner phenomenon or isomorphic response is named after the German dermatologist Heinrich Koebner (1838–1904) who first recognised it in psoriasis patients. It’s a phenomenon that causes skin lesions to appear at the site of a skin injury in otherwise healthy skin. These lesions have the clinical and histological features of the patient’s original skin disease; do not occur as a result of infection; do not occur as a result of allergic reaction to something coming into contact with the skin (Luo, 2014). 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, i.e. in lines (Ibid).

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. In July 2017, Koebner phenomenon was reported in a 68-year-old female patient with Sweet’s syndrome whose lesions developed on a linear scar (Chern et al, 2017).

Can it occur for reasons other than the health conditions mentioned above?

Yes. Koebner phenomenon can occur for lots of 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’s used to treat cancer, autoimmune conditions, and occasionally, Sweet’s syndrome (Luo, 2014; Verma et al, 2014). Click here to learn more.

What causes Koebner phenomenon?

We aren’t entirely sure what causes Koebner phenomenon. Current theories suggest that it’s 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 (Luo, 2014). The production of inflammatory substances such as cytokines and neuropeptides – small protein-like molecules used by nerve cells to communicate with each other – have been suggested as an initial step in a process that eventually leads to Koebner phenomenon (Luo, 2014; Yamamoto and Ueki, 2013). Chemical messengers such as nerve growth factor (NGF) may play a role, but this is still being investigated (Luo, 2014).

What is pathergy?

Pathergy, sometimes referred to as skin hypersensitivity, is an exaggerated skin injury that occurs as a result of minor skin damage (Oakley, 2011). It’s similar to Koebner phenomenon, but tends to occur within the context of neutrophilic dermatoses, particularly Behcet’s syndrome. It typically happens after a needle stick injury or similar injury, but also after minor skin damage such as a bump or bruise. The injury then leads to the development of lesions called papules (pimples or small bumps) or pustules (pimples or bumps containing fluid or pus), but a more severe injury, e.g. a surgical procedure, can sometimes result in ulceration. Unlike Koebner phenomenon, the lesions don’t always develop on healthy skin, and in neutrophilic dermatoses, can sometimes make existing skin lesions worse.

Apart from Behcet’s syndrome, in which conditions can pathergy be seen?

Pathergy can sometimes be seen in other forms of neutrophilic dermatosis, e.g. Sweet’s syndrome or pyoderma gangrenosum; inflammatory bowel disease; healthy individuals (Ibid).

What causes pathergy?

Pathergy is poorly understood, but when the outer layer of the skin is damaged, this causes activation of epidermal growth factor receptor (EGF-R) (Yamamoto and Ueki, 2013). This is a protein found on the surface of cells to which a substance called epidermal growth factor (EGF) binds. This then stimulates cell growth, cell production, and differentiation, the process where a cell changes into a more specialized cell-type. When EGF-R is activated, this in turn leads to the production of cytokines such as interleukin 8 (IL-8), which play an important role in causing neutrophilic dermatosis (Ibid).

Sweet’s syndrome and pathergy.

Pathergy is associated with Sweet’s syndrome. How many people with Sweet’s syndrome demonstrate pathergy?

In literature, pathergy is rarely reported in Sweet’s syndrome, but it’s known to occur in at least 8% of patients (Ginarte and Toribio, 2011).

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

In people with Sweet’s syndrome who demonstrate pathergy or Koebner phenomenon, skin lesions have been reported to have developed as a result of:

  • Cat scratches (Cohen, 2007).
  • Something that causes irritation when it comes into contact with the skin (contact dermatitis) (Cohen, 2007; Verma et al, 2014).
  • Skin damage caused by a biopsy, having blood taken, intravenous catheter placement (a small ‘tube’ placed in vein), or vaccination.
  • Insect bites.
  • Radiotherapy (Ibid).
  • Skin puncture while handling fish (neutrophilic dermatosis of the hands) (Gammoudi et al, 2017).
  • Sunburn (Cohen, 2007).
  • 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).
  • Food bolus injury (injury as a result of food getting stuck when you swallow). In 2016, the first case of oral pathergy affecting the mouth, tongue and pharynx was reported in a 68-year-old female patient (Klimpl et al, 2016).

What can you do to help yourself?

If you have problems with skin lesions developing as a result of skin damage, take care to avoid:

  • Sunburn.
  • Contact with irritants.
  • Scratching.
  • Ideally, surgical procedures should only be performed when the Sweet’s syndrome has settled down or is in remission. Debridement (removal of tissue, surgical or otherwise) of a 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’s 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 lesions. This is a debriding agent, and is being advocated as a treatment for Sweet’s syndrome by some alternative therapists. There is no evidence to support this claim, and it 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 irritates, 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.

  • Sweet’s syndrome is not caused by food allergy, and 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, then this should help to rule out other kinds of reaction.

  • If someone 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.

Further information.

Oakley, A. (2015) Acute Febrile Neutrophilic Dermatosis. DermNet NZ (online). Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1998. Updated September 2015. Accessed 18/03/18.

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 (PMC).


Chern, C., Royer, M. and Turnage, W. (2017) Sweet’s Syndrome Arising in a Scar. Case Reports in Dermatology, Jul;9:86–90 (Karger).

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

Gammoudi, R., Boussofara, L., Ghariani, N., Sriha, B., Belajouza, C., Denguezli, M. and Nouira, R. (2017) Neutrophilic dermatosis of the hands: an acral variant of Sweet’s syndrome or a distinct entity? European Medical Journal, Nov; 5(1):62-63 (online).

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

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 (Oxford Academic).

Luo, A. (2014) Koebner phenomenon. DermNet NZ (online). Author: Arcana Luo, Medical Student, University of Auckland, New Zealand; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, March 2014. Accessed 18/03/18.

Oakley, A. (2011) Pathergy. DermNet NZ (online). Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2011. Accessed 18/03/18.

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).

Yamamoto, T. and Ueki, H. (2013) Koebner Phenomenon in Rheumatoid Arthritis. Journal of Genetic Syndromes and Gene Therapy, Aug; 4:173 (OMICS).

2012-2018 Sweet’s Syndrome UK


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