Contact dermatitis

A 40-year-old woman presents to the office because of a rash and burning sensation on her hands. It started two days ago and is scaly and nonpruritic. She works as a gardener but recently started a new part-time house cleaning service near her neighborhood. Past medical history is significant for a streptococcal throat infection three weeks ago, treated with oral penicillin. She has taken warfarin regularly for the past three years after undergoing prosthetic aortic valve replacement. Family history is significant for atopic dermatitis in her mother. Vitals are within normal limits. Physical examination findings are shown.


Reproduced from Flickr

Which of the following factors most likely triggered this patient’s skin condition?