A 22-year old female with type 1 diabetes (T1DM) presented with generalized rash. She was diagnosed at the age of 9 years and is treated with insulin pump and CGMS (continues glucose monitoring sensors), her recent HbA1c was 7.4%. Four weeks prior to her rash presentation she started a low carbohydrate diet (50 gr of carbs per day) in order to improve her glycemic control. Pruritic erythematous papules, papulovesicular, and vesicles appeared on her axillary region, upper back and groins. Lesions were associated with severe pruritus and negatively affected her quality of life. Various therapies were initiated by dermatologist as: antifungal agent, Itraconazole, and Betamethasone Esters, without any improvement. Her serum beta-hydroxybutyrate levels were between 1.1-1.2 mmol/l. Prurigo pigmentosa, a rare pruritic inflammatory dermatosis secondary to her high ketones levels was diagnosed. Her condition resolved after she increased her carbohydrate intake to 75 gr per day. Beta-hydroxybutyrate level decreased concomitantly to 0.1-0.2 mmol/l. When carbohydrate restriction was rechallenged, she again entered ketosis, followed by recurrence of the pruritic lesions. Carbohydrate intake was increased and subsequently all lesions resolved with remaining reticular hyperpigmentation. During the last few years low carb diets have gained popularity among patients with T1DM. This case illustrates the rare side effect of high ketones body levels. Health care providers should be familiar with this side effect.