#1. SCABIES CAN LOOK LIKE ALMOST ANYTHING.
And the classic presentation of furrow lines between the fingers is rare (especially for norwegian scabies). In fact, scabies can accurately be described as "the great imitator". Here are some examples of the "non-classic" presentation of scabies:
#2. SCABIES REALLY ITCHES.
When you see a really itchy rash, scabies needs to be high in the differential. Other things in the differential include rhus dermatitis (i.e. from poison ivy), dyshidrotic eczema, and insect bites. I'm sure that are other itchy rashes in the differential but my mind is dull today.
#3. THE ENTIRE HOUSEHOLD NEEDS TO BE TREATED.
If one person has it, then it is likely that other people in the household have it. Dogs and cats in the home may need to be treated also.
#4. THE RASH TAKES UP TO 1-2 WEEKS TO RESOLVE
Although the mite is dead, it's poop "lives on" under the skin! So unless you want an angry phone call the next day from the patient wondering why the rash did not spontaneously resolve after an overnight application of Elimite Cream, make sure you inform the patient that the rash takes a while to resolve. Also, it's not a bad idea to retreat the household in 1-2 weeks.
#5. OTHER HOUSEHOLD MEMBERS DO NOT HAVE TO HAVE SCABIES FOR YOU TO MAKE THE DIAGNOSIS
Although the likelihood of scabies increases if other members have an itchy rash, that negative historical finding does not rule out your patient having scabies. It's all in the timing. Your patient may be the first in the household to demonstrate symptoms. Also some people also seem to develop a more rigorous allergic reaction to scabies than others. For example, five kids playing in a field of poison ivy will not all develop rhus with the same intensity—some who have never been exposed to poison ivy will likely not develop a rash at all.