Poison ivy, oak, and sumac

There are no definitive criteria to define mild, moderate, and severe dermatitis, but broad classification helps direct initial therapy. This is usually a clinical judgment based on:

• Symptoms of itch: some patients will complain significantly of itch with minimal signs, while others will tolerate extensive dermatitis. Very itchy rashes are more likely to become secondarily infected from excessive scratching and therefore may be treated as moderate to minimize this risk.

• Extent of disease: from a small localized area on one limb (mild end of spectrum) to extensive disease involving >30% of body area (severe).

• Severity of the dermatitis: mild erythema only (mild dermatitis) to large bullae formation (severe).

• Duration of dermatitis: 1-2 days to 10-20 days (mild to severe).

Very itchy dermatitis with large bullae, covering wide areas, and present for >1 week could be treated as severe. Small localized patches of mildly itchy erythema of a couple of days' duration could be treated as mild. Moderate dermatitis may have features of either or both these extremes.