Keto Rash | Causes, Symptoms, Diagnosis, and Treatment

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Keto rash is also known as prurigo pigmentosa, is a rare inflammatory dermatitis first described Nagashima et al, in 1971.

Prurigo pigmentosa has been characterized into three stages based on appearance and pathology

  1. Early-stage lesions: It is presented as pruritic urticarial plaques or papules that are characterized pathologically by superficial perivascular neutrophilic infiltrates.
  2. Fully developed prurigo pigmentosa lesions: It is manifested as crusted erythematous papules, papulovesicles with histology showing spongiosis and necrotic keratinocytes.
  3. Late-stage lesions: It evolves into smooth-surfaced pigmented macules with histological features of lymphocytic infiltrate and melanophages in the papillary dermis.

Prurigo pigmentosa has been linked to several conditions, including H. pylori infection and autoimmune diseases like Sjogren’s syndrome. In addition, it may also be associated with uncontrolled diabetes and those who fast or eat a ketogenic diet.

It primarily affects adolescents and young adults and the majority of patients diagnosed with prurigo pigmentosa are Asians, mostly women, however often misdiagnosed in Western countries.

Prurigo pigmentosa is characterized by erythematous papules and macules on the trunk, neck, and chest that resolve to leave a reticulate hyperpigmentation

Symptoms of keto rash include:

  • erythematous papules and macules on the trunk, neck, and chest
  • red spots, called papules, that take on a web-like appearance
  • a dark brown pattern left on the skin once the spots disappear

The etiology of prurigo pigmentosa is not well known.  It may be due to some endogenous and exogenous factors.

Endogenous factors

  • Keto diet
  • Starvation
  • Diabetes
  • Pregnancy
  • Helicobacter pylori infection

Exogenous factors

  • Sweating
  • Clothes rubbing against skin
  • Exposure to allergens such as para-amino compounds, trichlorophenol, chrome, and nickel

A case study published in the Turkish journal of pathology reported a 16-year-old female was on a strict diet and lost twenty kilograms within three months. She had a one-month history of pruritic rashes on her trunk and neck. Dermatological examination revealed excoriated erythematous papules on the neck, back, clavicular and intermammarian areas, as well as pale brown reticular hyperpigmentation on the front chest with increasing prominence at the intermammarian area. She was diagnosed with the early stage of prurigo pigmentosa.

During starvation or following a ketogenic diet, your blood glucose level drops due to which a ketogenic metabolism is initiated in your body. The ketone bodies namely acetoacetate, beta-hydroxybutyrate, and acetone that form as a result of this process pass from the blood into tissues and cell cytoplasms, joining metabolic processes within, or remaining around vessels to cause a perivascular inflammatory reaction.

A study showed that prurigo pigmentosa is a reactive inflammation associated with bacterial folliculitis as a frequent presence of bacterial colonies has been observed along with sequelae of inflammatory changes on biopsy.

A case study published in the Turkish journal of pathology reported a 16-year-old female was on a strict diet and lost twenty kilograms within three months. She had a one-month history of pruritic rashes on her trunk and neck. Dermatological examination revealed excoriated erythematous papules on the neck, back, clavicular and intermammarian areas, as well as pale brown reticular hyperpigmentation on the front chest with increasing prominence at the intermammarian area.

The histopathological examination of a punch biopsy from the back of the patient revealed neutrophils in the epidermis that was most widely spread, or grouped into clusters. Irregular acanthosis, dyskeratotic cells, spongiosis, neutrophilic and eosinophilic spongiosis in the epidermis was seen. The upper dermis revealed perivascular and interstitial infiltration of neutrophils, intermingled with lymphocytes, histiocytes, and a small number of eosinophils. Vascular proliferation and neutrophils within the lumina of some vessels were evident. She was diagnosed with the early stage of prurigo pigmentosa.

A study conducted on nine Chinese subjects diagnosed with prurigo pigmentosa concluded that prurigo pigmentosa is easy to misdiagnose. Histopathological characteristics can co-exist at different stages, consistent with the clinical finding that different stages of skin lesions presented concurrently, contributing to misdiagnosis.

No Treatment Required

If you have developed keto rash after going into nutritional ketosis, there is no need to panic. The rash most of the times resolves by itself within a few days or weeks. When I started following keto diet, I too developed keto rash. When I had a rash over my body, mostly on my neck, back, and chest I was not aware of the cause. I did a lot of research and learned that it could be due to a keto diet. However, I didn’t take any medicines and within few days it resolved by itself. May be in those days I was in deep ketosis, which could have led to keto rash.

Increase your Carbohydrate Intake Until No Longer in Ketosis

If you have developed a rash after starting keto diet, it could be due to very low carbohydrates in your diet. The simple way to treat the rash is to increase the number of carbohydrates to 50-90 gm per day in your diet.

Avoid Sweating

Since the acetone in sweat is a major rash trigger, it is best to keep yourself from sweating or at least avoid prolonged exposure to sweat. Try taking a few days off from the gym or reducing your workout intensity so you can minimize sweating. If you do sweat, be sure to shower directly after to wash off any perspiration.

Medicines

A literature review showed that oral minocycline is the first-line therapy for prurigo pigmentosa. However, doxycycline, macrolide antibiotics, and/or dapsone (diaminodiphenyl sulfone) may be indicated for some patients.

A recent study has demonstrated that colchicine may also be an effective agent in the treatment of prurigo pigmentosa since it exerts an anti-inflammatory effect by inhibiting neutrophil chemotaxis.

In a case report, a 16-year-old female was treated with 100 mg/day doxycycline. She reported complete relief from itchiness ten days after treatment. The treatment with doxycycline was continued for two months. It was observed that the existing papules resolved to leave brown hyperpigmentation.

A study showed that oral administration of minocycline is effective in the treatment of prurigo pigmentosa. Minocycline also effectively reduces the recurrence rate of prurigo pigmentosa. Another study also reported that minocycline is rapidly effective probably through its ability to scavenge reactive oxygen species and to inhibit the chemotaxis and neutrophil function.

Address Other Contributing Factors

The keto diet is a low carb high-fat diet. So we avoid most of the carbs and eat food which is rich in fat and protein. So if you are following keto diet, I am sure you must be eating more of eggs, dairy, nuts, seeds, fish, etc. Some of these foods may be allergic to so some individuals. I know a friend who is allergic to eggs, so he never eats eggs. So if you never had eggs and suddenly started having eggs, or any other food mentioned above which you have never consumed before could lead to allergic reactions. So if you can figure out the food which may be allergic to you, it’s better to avoid that food. It is advisable to consult a doctor and after proper diagnosis get the right treatment.

Many people following the keto diet might never get a keto rash. But if you are one of the unlucky ones, like me, please don’t panic. Most of the time it resolves by itself without any medications. There are several ways you can prevent keto rash. Some of them are listed below.

  • Gradually lower your carbohydrate intake. Rather than dropping your carbohydrate intake suddenly, try to taper carbohydrates out of your diet more slowly.
  • Supplement with a multivitamin/mineral initially. A once-a-day multivitamin or multimineral can help reduce the likelihood of nutrient deficiencies when you start the keto diet.
  • Consult with a doctor. There is no substitute for a consultation with a doctor. Always visit a doctor and get proper diagnosis and treatment. Many people avoid visiting the doctor and try to find a solution on the internet or by seeking advice from some keto group.

The keto diet drastically changes the way your body uses food for energy. These changes can lead to a range of side effects, including the keto rash. However, all side effects due to ketogenic diet are temporary. Once they subside in a couple of weeks’ time, you’ll only experience the benefits which make so many dieters return to keto eating again and again.

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