Why are some people's mosquito bites itchier than others'? New study hints at answer

Some people just can't stop scratching after they're bitten by a mosquito — but not everyone gets itchy after a bug bite or similar allergy-triggering encounter. Now, new research in mice pinpoints differences in immune system activity that may determine whether you end up itchy.

The skin is densely populated with sensory neurons, which are nerve cells that detect changes in the environment and then trigger sensations, such as pain, in response. When a person encounters a potential allergen, like mosquito saliva, these neurons detect it and may trigger an itchy sensation in response. They also help activate nearby immune cells, which kick off an iNFLaMMAtory reaction featuring swelling and redness.

Some people who are repeatedly exposed to an allergen can develop chronic allergic iNFLaMMAtion, which fundamentally changes the tissues where that iNFLaMMAtion is raging. For instance, the immune cells that respond to allergens can change the nerves' sensitivity, making them more or less likely to react to a substance.

"We all have sensory neurons, so we can all feel itchy — but not all of us get allergies, even though we're surrounded by the same allergens," senior study author Dr. Caroline Sokol, a professor of allergy and immunology at Harvard Medical School and Massachusetts General Hospital, told Live Science. "So what defines whose sensory neurons fire in response to allergens and whose don't?"

Related: Could allergies be 'deleted' someday?

To find out, Sokol and colleagues exposed mice to a chemical called papain, which causes an itchy sensation that makes mice scratch their skin. The different groups of lab mice in the study were missing different immune cells. The research, published Wednesday (Sept. 4) in the journal Nature, found that mice that lacked a specific type of T cell didn't scratch when they were exposed to papain.

The researchers wanted to find out how these cells, dubbed GD3 cells, drove sensory nerve responses. They grew GD3 cells in the lab and treated them with a chemical to make them release signaling molecules called cytokines. Then, they injected mice with normal immune systems with the cytokine-containing liquid the cells were grown in.