A skin reaction to an insect bite can be itchy and painful, and it can also be stressful wondering what might have bit you. From bed bugs to spiders, many bugs can bite and leave a rash. Fortunately, each of these skin reactions has unique characteristics. If you know what insect bite rashes look like, it can help you determine how to treat the area and how to avoid future bites. It can also help you figure out how to best ease your symptoms.
17 Different Insect Bite Rashes
A rash is an area of inflamed or irritated skin, and it can have various causes. Sometimes, it can be easy to confuse a bug bite rash with other conditions, such as fungal infections and common skin allergies, because it resembles one of them. The following descriptions and photos of rashes caused by common insect bites may help you learn to tell the difference.
Bed Bug Rash
Bed bugs bite humans and animals to feed off their blood. Not everyone reacts to bed bug saliva, but about 70% of people get an itchy rash. The wound can appear as one or more red bumps because bed bugs bite their victims several times in a night. The itchy rash often appears as a row or clusters of round, flat or raised red lesions at the site of the bites.
Substances in the saliva cause an allergic reaction, which contributes the way the rash looks. Itching begins about an hour after the bugs bite. For some people, the rash might not appear for days or a week depending on the body's reaction to the saliva, and the area might remain swollen for weeks before clearing.
Mosquito bites cause a local reaction and itching, and they are the source of more insect bites than any other bug worldwide. Their saliva contains toxins that cause a reaction in most people. The resulting rash may look like blisters or bruises and have a large area of swelling at the site, especially for people who are sensitive to mosquito saliva.
The bites can also cause other types of rashes depending on the disease the mosquito transmits, such as the widespread, red-mottled skin rash of dengue fever transmitted by the bite of the Aedes aegypti mosquito.
Chiggers are a type of insect that bites while in its larval form. The bites are most common in the summer and fall months, when the larva attaches to the skin to feed. Chigger mites attach to skin and inject their saliva into a bite, which might be painless at the time it happens. Angry-looking red bumps appear, and an allergic rash or welts can occur several hours after the chiggers attach. Itching can be severe, and the rash might only be present on areas which have been exposed to the sun.
The skin rash caused by the bite of the chigger mite is usually found around the ankles, the waistband of clothing, or in warm skin folds like the ones between toes and in the armpits. The bites often show up in groups of raised and very itchy welts. The bugs are most often present in grassy and wooded areas, and they tend to fall off the skin after a few days of feasting.
Dog or cat fleas can bite humans too. The resulting skin rash occurs because of an allergic reaction to the flea's saliva. The reaction looks like red bumps surrounded by small areas of inflammation. Fleas commonly bite on the feet and ankles, and the bites usually occur in groups.
The rash caused by these wingless bugs can itch for several weeks, and scratching creates a risk of infection in the area. In addition, flea-bourne infections are becoming much more prevalent. There are a number of diseases caused by fleas, so if you develop symptoms other than an itchy rash, it's important to talk to a doctor.
Ticks live on deer, squirrels, horses, and other animals, but they can latch on to humans to feed on their blood. Often, you may notice the tick embedded in your skin, surrounded by a red area. Ticks can be very small, however, making them difficult to notice. Tick bites may feel irritated, but they rarely itch.
Ticks can carry bacteria, which cause conditions such as Rocky Mountain spotted fever and Lyme disease. The rash of Lyme disease might develop one to four weeks after a tick bite. It looks like a flat, round patch with a bulls-eye that may increase in size over a few days and several of these patches might be present. The central bulls-eye is the site of the tick bite from which the rash spreads out. If you suspect that you were bitten by a tick after being outdoors and develop a rash, fever, and muscle and joint pains, seek medical attention. Lyme disease infection can lead to serious illness.
Scabies Mites Rash
Scabies are insect-like bugs, which burrow under the skin after they bite. They occur all over the world and spread easily from one person to another. They cause multiple red bumps, pustules, or vesicles which are very itchy and can crust over when they drain. Small, red lines mark these mites' under-the-skin tracks.
Common sites of bites include in between the fingers, on the wrists and arms, on the buttocks, and in the groin. The intense itching can be worse at night due to substances secreted by the mites and the eggs they lay under the skin.
Lice commonly infect the scalp, pubic area, and other parts of the body, and they can leave small bite marks on visible areas including the neck and shoulders. While the bites aren't always visible, they can be extremely itchy. Scratching can cause redness and eventually, a thickened area on the skin. The area can become infected from scratching.
Body lice are more common in populations that don't have access to bathing facilities, but head lice can infest any population. Both can be difficult to diagnose, so if you have itching, it's worth checking with your doctor.
Horse Fly Bites
Horse flies bite horses and other large animals, sometimes including humans. They're a large fly - often between 0.5 and 1.25 inches in length. The females bite and suck blood, and a weal appears at the site of the painful bite. The bites tend to appear alone.
The bites themselves may not itch, but some people develop a local allergic, red rash or bigger fluid-filled welts. A more severe reaction causes body hives, wheezing, dizziness, and other systemic symptoms, although this is rare.
Black Fly Bites
Black flies also feed on the blood of animals and humans, and their prevalence may be increasing. These flies tend to bite the ears, neck, and ankles where the skin is thinner. The bite might be painless, but it can leave a small, itchy red puncture at the site or larger swelling around the area.
A bigger reaction to the fly's saliva can cause systemic symptoms such as fever, headache, and joint pains. Black flies can also transmit other organisms such as the parasitic worm that causes river blindness, which usually occurs only in tropical areas.
The biting midge fly lives near water and damp locations and can attack animals and humans. Their bites can cause severe itching at the site. A local allergic reaction to the midge's saliva raises a small red welt.
Some species of midges can transmit viruses, worms, and other pathogens to their victims. However, this is very uncommon and isn't a public health concern in the US.
Brown Recluse Spider Bites
The brown recluse spider usually inhabits dark spaces such as closets, attics, basements, and sheds. This spider's bite is often painless, but it creates a reddish or purplish bulls-eye rash or bruise within a few hours. The skin can blister, rot, and then form a blackened ulcer at the center of the rash.
The toxins in the spider's venom can also cause itching, swelling, and pain at the site, as well as general muscle aches, nausea, and vomiting. Seek medical attention as soon as possible if you suspect you were bitten by a brown recluse.
Bites From Black Widow Spiders
Black widow spiders tend to hide outdoors in holes, wood piles, and tree cuttings. The bite looks like two red puncture marks in the victim's skin, and the rash is limited to two small areas of inflammation around the marks. This spider's bite is often painless, but pain can set in soon after.
The venom the spider injects in the skin is poisonous, so seek medical attention immediately after a bite. It can affect a person's nervous system and cause seizures and severe symptoms in other organs such as abdominal pain, vomiting, muscle weakness, or difficulty breathing.
Yellow Sac Spider Bites
The yellow sac spider is found outdoors in shrubs, trees, under rocks, and hiding indoors. It's believed this species causes most of the bites attributed to spiders, and its painful bite also has a burning sensation.
The spider's fangs leave two reddish puncture wounds which can form a hard lump or blisters. The skin around the bite breaks down, dies, and then heals itself. As with any suspected spider bite, it is helpful to collect the bug so it can be identified.
Biting isn't the only way bugs can cause rashes. Their stings can also affect the skin, and bee stings are among the most common. An individual's reaction to a bee sting can vary from mild to severe. It can cause an itchy, tender welt, and a small, whitish area often surrounds the bump.
A greater allergic reaction to the bee's venom causes a red rash to occur around the immediate area, and a more severe reaction is possible if a person was stung before. The most severe systemic allergic, anaphylactic reaction to a sting can become a medical emergency which could lead to cardiac arrest and death. Symptoms include whole body hives, difficulty breathing, sweating, dizziness, and nausea, and loss of conciousness. Immediate treatment with epinephrine injections can prevent a fatal outcome.
A wasp sting can cause a severe allergic reaction as well. Like bee stings, a wasp sting can also cause the victim to have a serious systemic, anaphylactic reaction which requires emergency treatment with epinephrine. However, most people do not have an allergy to wasps.
In people who aren't allergic, a red rash will appear at the site and swelling, pain and itching might also occur in the area of the sting.
The sting of a scorpion can produce a small, painful swelling which itches. An allergic reaction can also occur in people who were previously sensitized to a scorpion bite. Allergic symptoms include skin hives and difficulty breathing, similar to anaphylactic reactions to other bugs.
Venomous scorpions can also cause vomiting, disturbed vision, and difficulty breathing. Their sting is a serious medical emergency.
Fire Ant Stings
Fire ants cause painful, flat red lesions or pus-filled blisters or pustules which erupt at the sites of the stings. A typical allergic reaction to the venom can cause a red rash and swelling around the bumps. Victims feel an intense burning when stung, and the lesions become itchy soon after.
Topical antihistamine creams, steroid creams, or oral steroids are used to relieve the symptoms until the rash resolves. A systemic, anaphylactic reaction can also occur and is treated with epinephrine injections.
Home Rash Treatments
Some rashes can resolve in a few hours to a few days without treatment. There are several ways relieve some of the symptoms.
- Hold ice or cool compresses on the rash area.
- Appy a topical anti-itch ointment or lotion, such as Benadryl (diphenhydramine) or Calamine lotion, to reduce the itching.
- Home remedies such as applying a baking soda paste or a solution of meat tenderizer and water can help ease pain and itching.
- Try not to scratch the rash to avoid further irritation, increased itching, more pain, or ulcer formation and infection with bacteria.
When to Seek Medical Attention
Consult a doctor if the rash or skin reaction to a bite or sting is large or spreading or significant local symptoms are not relieved by home remedies. Seek urgent medical attention if you develop a generalized body rash or other symptoms of a systemic, anaphylactic reaction such as headache, shortness of breath, nausea or vomiting, or lightheadedness. Most stings and bites resolve on their own, but it's important to keep an eye on your symptoms.