Have you ever wondered why mosquito bites itch? Sometimes you get bitten and it only itches a little bit, while other times a bite makes you itch uncontrollably. Here is an explanation of why mosquito bites itch, why all bites aren’t the same, and what you can do to get relief.
Why Do Mosquito Bites Itch?
- Mosquito bites itch because mosquito saliva contains chemicals that produce inflammation.
- In some cases, components of mosquito saliva cause an itchy allergic reaction.
Female mosquitoes bite so they can get the blood meal they need in order to lay eggs. But, they can’t just jab you and use their mouthparts (proboscis) like a straw to suck up blood. Blood clots too readily, plus the body’s immediate immune reaction to the injury can stifle the flow. So, mosquito saliva (their “spit”) contains compounds that reduce the aggregation of blood platelets, slow clotting, reduce blood vessel constriction, stimulate inflammation, and alter the body’s immune response. Additionally, the saliva contains enzymes that digest sugars and antimicrobial agents.
Because all mosquito saliva stimulates inflammation, all bites have the potential to itch. Inflammation is a nonspecific response that everyone suffers from a mosquito bite. However, the proteins and polypeptides in mosquito saliva also trigger an allergic response from binding IgG and IgE antibodies. Both immediate and delayed hypersensitivity reactions can occur, producing itching, swelling, and redness.
Why Different Mosquito Bites Don’t Itch the Same Amount
Some mosquito bites itch more than others. To some extent, the degree of itching from inflammation depends on where you get bitten and how many bites you have. But, the big difference between an annoying bite and one that drives you insane with itchiness is whether or not you have an allergic reaction to the mosquito’s saliva and how serious that reaction is.
- Because each species contains its own cocktail of chemicals in its saliva, you react differently depending on what kind of mosquito bites you.
- You adapt somewhat to common mosquitos in your environment. If you get bitten by a different type of mosquito than usual, you’re more likely to react to it with itchiness.
- The state of your immune system at the time of the bite plays a role in how much you’ll itch.
Skeeter Syndrome
Skeeter syndrome sounds like a made-up phrase, but it’s the name of a real medical condition that is characterized by an allergic reaction to a bite that causes inflammation, peeling skin, and sometimes hives and a fever. The syndrome resembles cellulitis and other skin infections, but a diagnostic test can identify the mosquito allergy. The bad news is that you’ll probably itch a lot if you’re prone to skeeter syndrome. The good news is that oral antihistamines like cetirizine (Zyrtec) and diphenhydramine (Benadryl) are effective against the symptoms.
Severe Mosquito Bite Allergy or SMBA
Another potential reaction to a mosquito bite is called severe mosquito bite allergy or SMBA. Itching is only the tip of the iceberg. SMBA is a serious immune reaction to a mosquito bite that causes redness, swelling, and eventually ulcers or necrosis at the bite site. The reaction sometimes causes fever, fatigue, and problems with the liver and/or spleen. SMBA affects people who are highly allergic to mosquito saliva, those with a lymphoid disease like lymphocytic leukemia or mantle cell lymphoma, and about a third of persons with an active Epstein-Barr virus infection.
How to Stop Mosquito Bites From Itching
If you’re bitten, the Centers for Disease Control (CDC) first recommends you wash the affected area with soap and water. There are several ways to stop mosquito bites from itching:
- Apply a cold compress or ice pack to the bite for 10 minutes and reapply as needed. The cool temperature reduces inflammation and thus reduces itching.
- Use an over-the-counter antihistamine or anti-itch cream or gel. Follow the instructions on the product label.
- Apply a paste of baking soda (sodium bicarbonate) and water. Leave the paste on the bite for 10 minutes and rinse it off. Reapply as needed, but discontinue the treatment if your skin gets irritated. Baking soda is a weak base that reacts with some components of insect saliva and inactivates them.
Aside from the CDC recommendations, there are other anti-itch options:
- Take an over-the-counter antihistamine if you are an allergy-sufferer susceptible to bites. Relief takes longer to set in, but also lasts longer.
- Press an “X” into the bite with a fingernail. This works temporarily because the body feels either pain or itching, but not both at the same time. Be warned, however, that the itch can return worse than ever once the discomfort of the “X” fades.
- Apply toothpaste, soap, or another common household base. Really, baking soda is your best bet here. The other options work in a pinch, but are more likely to irritate your skin.
No matter how tempted you are, don’t scratch the bite. Scratching can lead to an infection, which also itches and leads to complications.
References
- Grossman, G.L.; James, A.A. (1993). “The salivary glands of the vector mosquito, Aedes aegypti, express a novel member of the amylase gene family”. Insect Molecular Biology. 1 (4): 223–32. doi:10.1111/j.1365-2583.1993.tb00095.x
- Kyriakidis, I.; Vasileiou, E.; Karastrati, S.; Tragiannidis, A.; Gompakis, N.; Hatzistilianou, M. (December 2016). “Primary EBV infection and hypersensitivity to mosquito bites: a case report”. Virologica Sinica. 31 (6): 517–520. doi:10.1007/s12250-016-3868-4
- Pérez-Vanzzini, R.; González-Díaz, S.N.; et al. (2015). “Hipersensibilidad a la picadura de mosquito manifestada como síndrome de Skeeter” [Hypersensitivity to mosquito bite manifested as Skeeter síndrome]. Rev Alerg Mex. 62(1):83-7. PMID: 25758116.
- Ribeiro, J.M.; Francischetti, I.M. (2003). “Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives”. Annual Review of Entomology. 48: 73–88. doi:10.1146/annurev.ento.48.060402.102812
- Simons, F.Estelle R.; Peng, Zhikang (1999). “Skeeter syndrome”. Journal of Allergy and Clinical Immunology. 104 (3): 705–7. doi:10.1016/S0091-6749(99)70348-9