Johns Hopkins suggests SCRATCH method for diagnosing insect bites in kids

The Johns Hopkins University Gazette (11 September 2006) reports that the Johns Hopkins Children’s Center has come up with a helpful acronym for doctors in diagnosing the source of childrens’ rashes. It highlights features of bed bug bites and other conditions, which many of us adults who suffer from bed bug bites have also encountered.

Called SCRATCH –the letters form a memorable acronym for symmetry, cluster, Rover, age, target/time, confused, household) – it is a guide to the symptoms and features that help pediatricians and others to recognize the source of a rash.

Insect-bite skin rashes mimic the symptoms of a variety of conditions, ranging from fungal infections, scabies, allergies and environmental contacts to HIV-associated dermatoses. Reactions to a bite are often delayed, making it difficult to trace exposure.

“SCRATCH could spare many children and their parents from going through invasive, not to mention expensive, procedures if pediatricians recognize the problem early on,” said Raquel Hernandez, a third-year resident at the Children’s Center and lead author of the article, published in the July online edition of Pediatrics.

Hernandez and co-author Bernard Cohen, associate professor in the School of Medicine and head of dermatology at the Children’s Center, developed SCRATCH by examining a month’s worth of patient records from visits to the Children’s Center dermatology clinic. They found that the majority of children who were eventually diagnosed with an insect-bite rash had undergone extensive lab tests and skin biopsies before they were referred to Johns Hopkins.

The most common misdiagnosis was scabies, a skin infection caused by a parasite that produces red, itchy lesions. Many of the children were treated repeatedly for scabies.

“These guidelines are really intended to make pediatricians consider insect-bite hypersensitivity as a diagnosis and think twice before referring a child for a skin biopsy or another invasive procedure,” Cohen said.

My doctor did not hesitate to prescribe Elimite for Scabies, which she could have ruled out with a simple skin scraping. Instead, the Elimite gave me a bad reaction, and my “mysterious rash” did not disappear.

Here’s how SCRATCH works, and keep in mind, it’s all applicable to adults too:

Using the tool is straightforward, Cohen said. If the rash fits the SCRATCH criteria, it’s likely bug-borne. The seven checkpoints are:

S for symmetry. Erruptions are usually symmetric and appear on exposed parts of the body, such as face, neck, arms, legs. Younger children may have rashes on their scalps. Diaper areas, palms and soles are not affected. The trunk is rarely affected. By contrast, scabies causes rashes on palms, soles and between toes and fingers.

Keep in mind that you can get single bed bug bites, as well as bites on any part of your body (though the scalp is rarely troubled: they don’t like going through hair). You can get bed bug bites, therefore between toes or fingers, on palms, etc. But they’re not the hotspots they are with scabies.

C for clusters. Lesions appear in “meal clusters,” described as breakfast, lunch and dinner. The linear or triangular clusters are typical of bedbug bites but also appear in bites caused by fleas.

As above, bed bug bites do come in singles. You are likely to see at least some clusters.

R for Rover not required. Presence of pets in the household is not a criterion for diagnosis because a bite might occur outside of the home.

You need not have pets to have fleas or bed bugs.

A for age specific. The condition is most prevalent in children between the ages of 2 and 10.

I am not sure about this one, actually. Most of the bedbuggers are allergic to bedbugs and we’re all grown up.

T for target lesions and for time. Target-shaped lesions – so named for their resemblance to the bull’s-eye on a target — are typical of insect-bite hypersensitivity. Time indicates the chronic/recurrent nature of the eruptions. Many patients may have delayed reactions and may not experience flare-ups until months or years after the initial exposure. Most children develop full immunity by age 10 and no longer have recurrent rashes.

C for confusion. Parents often express confusion and disbelief at the suggestion that there might be fleas or bedbugs in their homes. “One of the primary criteria is that if the parents don’t believe me, I am probably right,” Cohen said.

Forget parents: my doctor expressed said confusion. She said if I had bed bugs I’d see them. Not always as soon as you’re suffering, and for me, many months of suffering without a sighting.

H for household with single family member affected. Unlike conditions that have similar symptoms, such as scabies and atopic dermatitis, insect-bite rashes often appear in a single member in a family.

“Common sense might tell us that fleas and mosquitoes would affect other members of the family, but we must keep in mind that these rashes develop in children who have hypersensitivity that others do not have,” Hernandez said.

This one is very telling: if you have scabies, those in close physical contact with you will too, at least in short order.

Bed bugs can trouble one in a household. They can even trouble no-one in a household. Which is why my neighbors can have given them to me and have no clue they have them.

Hopefully SCRATCH is a start towards doctors better recognizing the growing incidence of bed bug bites in kids. But hopefully all doctors will soon have more relevant knowledge for diagnosing various skin problems.