Solve the Medical Riddle: She Had a Rash on Her Arms and Then New Patches Started Appearing on Her Legs, Fourth Week

Editor’s note: Welcome to our ThirdAge feature that gives you a chance to play medical sleuth as we share the details of what happened when a patient presented with a problem that stumped the physician at first.

The first week of this riddle, the patient reported her symptoms to an Urgent Care doctor who referred her to a dermatologist. The second week, the dermatologist proceeded with the examination using the first three components the classic S-O-A-P notes, which is as follows:

S=Symptoms or Chief Complaint

O=Objective Findings

A=Assessment or Analysis

P=Treatment Plan or Recommendations

Last week, we let you know what some people had suggested as possible diagnoses. This week, the doctor will move on to <strong>P</strong> to reveal the actual diagnosis. Then we’ll begin a new riddle for the following month!

The Dermatologist Reveals the Diagnosis

All of the guesses that people made last week were good but Lorraine K. is the one who came closest to the actual diagnosis. She never received a diagnosis herself, but she probably did have the same condition that the dermatologist said Cynthia had: an id reaction to dermatitis, also called autosensitization. As the dermatologist put it, “Your immune system goes haywire”. That’s why Cynthia kept getting new patches of rash all over her body, even in places where she probably hadn’t touched an allergen.

While the exact cause of the id reaction is unknown, the following factors are thought to be responsible:

1. abnormal immune recognition of self skin antigens

2. stimulation of normal T/inflammation cells by altered skin constituent such as the antigen from the fern touching skin

3. lowering of the irritation threshold

4. blood/hematogenous spread/dissemination of cytokines/inflammatory enzymes from a primary site such as where the fern touched the skin

5. People Cynthia’s age sometimes have weakened immune systems and shingles is a rash that develops due to a weakened immune system. However, an id reaction is not caused by a weakened immune system. Rather it is a sign of an over-reactive immune system.

6. The id reaction doesn’t mean the actual fern material is “spreading”, but the body develops widespread response just the same.

The dermatologist said that she would do skin patch tests down the road if the treatments she was going to prescribe for Cynthia didn’t work but that she was confident the treatments would be sufficient.


1.    Oral OTC antihistamines (Allegra or Claritin)

2.    Oral diphenhydramine and cholpheniramine in sedating cold medicines

(Benadryl, Dramamine) can relieve itching but should be taken at night because they cause drowsiness.

3.    Avoid applying antihistamine lotions to the skin because you may have allergic contact dermatitis from the lotion itself.

4.    For mild cases that cover a relatively small area, over-the-counter 1% hydrocortisone cream may be sufficient but in Cynthia’s case, a prescription-strength cream was appropriate.