Cockroaches tend to get a bad rap. As repulsive an animal as they are to many people, the disease that they inflict on us is minimal compared to other insects like mosquitoes or fleas. In fact, although most dermatology books have whole chapters on insects that cause skin diseases, the infamous cockroach is rarely mentioned.
Now, if you have ever seen a cockroach scamper across the floor and felt yourself develop a rash, you are not crazy. Although they do not often transmit diseases, cockroaches do have potent antigens that can trigger eczema. These antigens are proteins that when they contact human skin trigger an inflammatory response. The antigens from cockroaches are similar to antigens from dust mites (a notorious instigator of allergy).
When they contact the skin, the antigens activate a receptor in the skin that causes inflammation. The inflammation also causes an itching sensation and inhibits your skin’s ability to heal.
It is well known that allergens from cockroaches can make asthma worse. Over 1/3 of of people who live in cities and have asthma are allergic to cockroaches. We also knew that some people develop a rash if a cockroach crawls on their skin. (How some people can sit still while a cockroach crawls on their skin is still unknown to science).
Specifically, cockroaches can trigger a skin condition called atopic dermatitis. Atopic dermatitis is another name for eczema — it is an itchy red rash that develops most often in childhood. In most people, eczema improves with age. Atopic dermatitis develops when the skin’s normal protective barrier is disrupted and the body’s immune response is overly aggressive. The rash from atopic dermatitis is often red and scaly and appears mostly on the neck, folds of the arms and legs, and the face.
A recent study published in the Journal of Investigative Dermatology studied the effect of cockroach allergens on the skin. They found that both cockroach allergens as well as dust mite allergens caused a breakdown in the protective barrier of the skin after just 3 hours of exposure. By breaching your skin’s exterior defences, the allergens can easily trigger an inflammatory response that leads to a red, itchy rash that can last weeks or more.
To prevent this eczema trigger, I would suggest you avoid cockroaches.
If it is impossible for you to avoid cockroaches (which is the case in many cities), then keeping your skin protected with a good barrier cream is important. Any ointment (such as Vaseline) or a cream that contains silicone such as Eucerin Intensive Repair Body Creme, can provide a good barrier to prevent allergens from entering your skin and block the triggering of eczema.