ConditionSkin, hair & nails
Insect Bites and Stings
Insect bites and stings usually cause a small, itchy or painful red bump that settles within a few days. Washing the area, a cold compress, and an antihistamine or hydrocortisone cream are usually all you need. The rare dangers are a severe allergic reaction (anaphylaxis), which needs epinephrine and a 911 call within minutes, a bacterial skin infection, and diseases carried by mosquitoes and ticks. Knowing which insect bit you and watching how the area changes over 48 hours tells you most of what you need.
Also called: Bug bites, insect stings, arthropod bites, bee or wasp sting, mosquito bite
At a glance
- Usual reaction
- A red, itchy or stinging bump that fades in 1 to 3 days.
- Large local reaction
- Swelling over 4 inches (10 cm) that peaks at 24 to 48 hours and lasts up to 10 days. Not an infection, and not usually dangerous.
- Emergency
- Anaphylaxis: throat tightness, wheezing, widespread hives, dizziness within minutes.
- Home care
- Wash, cold pack, antihistamine, hydrocortisone cream, do not scratch.
- Infection signs
- Spreading redness, warmth, pus and fever, usually 2 or more days after the bite.
When to get help
Call 911 or go to the ER
- Trouble breathing, wheezing, throat or tongue swelling, hoarse voice, faintness or widespread hives after a sting or bite: use an epinephrine auto-injector if available and call 911 or your local emergency number
- Dozens of stings at once, or a sting inside the mouth or throat
- Severe pain, cramps or sweating spreading from a bite, which may be a black widow spider
See a doctor within a day or two
- Redness that keeps spreading after 48 hours, red streaks, pus, or fever, which suggest infection
- A bite that turns into a dark blister or open sore, which may be a brown recluse spider
- A bull's-eye rash, fever, aches or a facial droop days to weeks after a tick bite
- Fever, headache, rash or joint pain after mosquito bites while traveling
Book a routine appointment
- A previous whole-body reaction to a sting, to discuss allergy testing, venom immunotherapy and an epinephrine prescription
- A tick that was attached for more than 36 hours in a Lyme disease area
- Itchy bites that keep appearing at home, which may be bed bugs, fleas or scabies
Usually safe to manage at home
- A small red, itchy or sore bump, or swelling around the bite without fever
First aid for bites and stings
- Move away from the area to avoid more stings.
- Remove a stinger (honeybees leave one) quickly by scraping it out with a fingernail or card edge. Speed matters more than method.
- Remove a tick with fine-tipped tweezers: grip close to the skin and pull straight up with steady pressure. Do not twist, burn or smother it.
- Wash with soap and water.
- Apply a cold pack wrapped in a cloth for 10 to 20 minutes to reduce pain and swelling.
- Raise a swollen arm or leg.
- Relieve itching with hydrocortisone 1% cream, calamine lotion or an oral antihistamine (non-drowsy by day, follow the label dose).
- Ease pain with acetaminophen (paracetamol) or ibuprofen, following the label dose. No aspirin for children or teenagers.
- Do not scratch. Keep nails short, and cover the bite if a child picks at it.
Types of reaction
| Reaction | What it looks like | Timing | What to do |
|---|---|---|---|
| Normal local | Small red bump, itch or sting | Minutes, lasts 1 to 3 days | Home care |
| Large local | Swelling over 4 inches (10 cm), may involve a whole limb | Builds over 24 to 48 hours, lasts 5 to 10 days | Cold, antihistamine, see a doctor if severe |
| Infection (cellulitis or impetigo) | Spreading redness, warmth, pain, pus or honey-colored crusts | Usually 2 or more days after | See a doctor, may need antibiotics |
| Anaphylaxis | Hives, swelling, breathing trouble, vomiting, faintness | Usually within 5 to 30 minutes | Epinephrine and 911 |
A large local reaction is often mistaken for infection. Swelling that appears within hours and is itchy rather than increasingly painful is almost always allergic swelling, not infection.
Common culprits and their clues
- Mosquitoes: itchy pink bumps on exposed skin, often after dusk. Can transmit West Nile, dengue, Zika and malaria in some regions.
- Bees, wasps, hornets and yellow jackets: immediate sharp pain, then a red swollen welt. Honeybees leave a stinger. Wasps can sting repeatedly.
- Fire ants: clusters of stings that form white pus-filled bumps within a day. Do not pop them.
- Fleas: small itchy bumps in groups, usually around the ankles and lower legs. See flea bites.
- Bed bugs: itchy bumps in a line or cluster of three ("breakfast, lunch and dinner") on skin exposed during sleep. See bed bug bites.
- Ticks: usually painless. The tick may still be attached. Can transmit Lyme disease and other infections.
- Biting flies, midges and no-see-ums: painful or very itchy bumps, sometimes with a tiny central blood spot.
- Chiggers: intensely itchy bumps around the waistband, ankles and skin folds after walking in grass.
Spider bites are much rarer than people think. Many "spider bites" are actually skin infections. True dangerous bites are covered under envenomation from spider bites.
If new itchy bumps keep appearing in the same household, think of bed bugs, fleas from pets, or scabies, which is a mite that burrows rather than bites.
Allergic reactions to stings
Insect sting allergy causes anaphylaxis in up to about 3% of adults. Symptoms beyond the sting site include:
- Hives or flushing over the body
- Swelling of the lips, tongue or throat
- Wheezing, coughing or shortness of breath
- Dizziness, fainting or a weak, fast pulse
- Nausea, vomiting or cramps
Use an epinephrine auto-injector immediately if you have one, then call 911, even if symptoms improve. See anaphylaxis for full first aid. Afterward, an allergist can test for venom allergy. Venom immunotherapy (allergy shots) greatly reduces the risk of a future systemic reaction, to roughly 5% to 10% or less, and is recommended for people who have had a systemic reaction.
How bites are diagnosed
Most bites are diagnosed by their look, location and your history: where you were, what time, whether others or pets are affected. Blood tests are only used for suspected tick-borne or mosquito-borne infections, and allergy tests after a serious reaction.
Preventing bites and stings
- Use an EPA-registered repellent such as DEET, picaridin, IR3535 or oil of lemon eucalyptus (not on children under 3 years). Apply sunscreen first, then repellent.
- Treat clothing and gear with permethrin for hiking and camping.
- Wear long sleeves, long pants and socks in tick or mosquito areas, and check for ticks daily.
- Empty standing water around the home.
- Avoid perfumes and bright, flowery clothing near stinging insects, cover drinks outdoors, and keep food covered.
- Treat pets for fleas and ticks.
- If you have a sting allergy, carry two epinephrine auto-injectors at all times.
Frequently asked questions
How do I know if an insect bite is infected?
Signs of infection include redness and pain that keep increasing after 48 hours, warmth, pus, red streaks spreading from the bite, swollen glands and fever. Itchy swelling that appears within hours is more likely an allergic reaction than infection.
Why is my bug bite swelling so much?
Large local reactions are common, especially with mosquito and bee stings in children. The swelling can cover a whole hand or forearm and peaks at 24 to 48 hours. Cold packs, raising the limb and an oral antihistamine help. It is not dangerous by itself.
When should I worry about a bug bite?
Seek emergency help for breathing trouble, throat swelling, widespread hives or faintness. See a doctor for spreading redness after 2 days, fever, red streaks, a bite that becomes a dark sore, or a bull's-eye rash or flu-like illness after a tick bite.
What is the best thing to put on an insect bite?
Wash the bite, apply a cold pack, then hydrocortisone 1% cream or calamine lotion for itch. An oral antihistamine helps with itching and swelling. Avoid scratching. Antibiotic cream is only needed if the skin is broken and showing early signs of infection.
How long do insect bites last?
Most bites fade within 1 to 3 days. Large local reactions can last 5 to 10 days. Fire ant pustules and chigger bites may itch for a week or more. A bite that lasts longer than 2 weeks or keeps growing should be checked.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: How to treat bee stings; Bug bites and stings
- CDC: Mosquito bite prevention; Tick bites
- American Academy of Allergy, Asthma & Immunology: Stinging insect allergy
- NHS: Insect bites and stings
- Mayo Clinic: Insect bites and stings first aid