Scratching a bug bite or rash may seem irresistible, but it'll only provide temporary relief and likely prolong the itch, researchers found.
Scratching is a natural response to a skin irritant that increases skin inflammation and can make certain diseases, such as eczema, worse.
Researchers at the University of Pittsburgh investigated the relationship between itch, scratching, and inflammation by applying an allergen to the ears of mice to trigger allergic-contact dermatitis, an eczema-like inflammatory skin condition.
The mice that developed the skin reaction were divided into two groups: one that was allowed to scratch freely and another that was prevented from scratching with an Elizabethan-style collar.
The researchers found that scratching activated mast cells, which release histamine and other inflammatory chemicals that cause itchiness.
The mice that scratched freely released more substance P, a signaling molecule that activated more mast cells, causing increased inflammation and a prolonged itch-scratch cycle.
Conversely, the mice that were prevented from scratching and those lacking the itch-sensing neuron experienced less inflammation.
The researchers also found that scratching reduced levels of staphylococcus aureus, one of the bacteria most associated with skin infections.
However, they cautioned that the damage that scratching does to the skin probably outweighs this benefit when itching is chronic.
The study resolves a paradox: if scratching an itch is bad for us, why does it feel so good?
The researchers suggest that scratching provides defense against bacterial skin infections, which may explain why scratching is often pleasurable.
Cold compresses and 1% hydrocortisone cream may help relieve itching, according to dermatological advice.
