Spider bites

Spiders usually bite when they are trapped against the skin, disturbed, or handled. Most bites cause only a small area of pain, redness, or swelling. Some do not inject venom at all.

A few spider species can cause more serious illness. These include widow spiders, recluse spiders, and Australian funnel-web spiders. The medically important species differ by region. A bite blamed on a spider may also turn out to be an insect bite, skin infection, allergic reaction, or another skin condition.

Widow venom mainly affects nerves and muscles. It can cause intense pain, sweating, and muscle cramps. Recluse venom can damage skin and, less often, red blood cells or other organs. Funnel-web venom can rapidly affect breathing, muscles, and the nervous system.

It is often impossible to confirm a spider bite unless the bite was witnessed and the spider was identified. A new sore with no spider present should not automatically be assumed to be a spider bite.

A minor bite may cause:

• A brief stinging or pinprick feeling
• A small red, raised, or swollen area
• Itching or tenderness
• Mild pain around the bite

These symptoms often remain limited to the skin. Two puncture marks are sometimes described, but they are not a reliable way to identify a spider bite.

A widow spider bite may be painless at first or feel like a pinprick. Pain can then spread from the bite into the abdomen, back, chest, or limbs. Muscles may become tight or cramp strongly. Other symptoms can include sweating, nausea, vomiting, headache, restlessness, and a fast heartbeat. Severe abdominal tightening can resemble a serious abdominal illness.

A recluse spider bite may cause little discomfort at first. Pain can increase over several hours. The area may become red, pale, bruised-looking, or blistered. In some cases, a blue or purple area develops as skin tissue is injured. An open sore may form over the following days.

Rarely, a recluse bite causes illness beyond the skin. Possible symptoms include fever, weakness, nausea, dark urine, pale skin, or yellowing of the eyes or skin. These may indicate the breakdown of red blood cells, called hemolysis, and need urgent assessment.

Australian funnel-web bites can cause rapid pain, heavy sweating, drooling, vomiting, muscle twitching, breathing difficulty, or confusion. A suspected funnel-web bite is an emergency even if symptoms have not yet appeared.

Spiders do not usually seek people out to bite them. A bite is more likely when a spider is pressed against the skin inside clothing, shoes, gloves, towels, or bedding. Bites may also happen while moving stored boxes, firewood, outdoor furniture, or building materials.

Widow spiders often live in sheltered, undisturbed places such as sheds, woodpiles, garages, and outdoor equipment. Recluse spiders favor dry, quiet spaces, including storage areas and clutter. However, recluse spiders live only in certain geographic regions. A recluse bite is unlikely in a place where these spiders are not established.

Funnel-web spiders occur in parts of Australia. They may be found in cool, damp, sheltered areas and can enter homes, swimming pools, shoes, or clothing.

The seriousness of a bite is influenced by the spider species, the amount of venom injected, the bite location, and the affected person's age and health. Children and older adults may be more vulnerable to the whole-body effects of some venoms.

There is no routine blood test or skin test that confirms most spider bites. Diagnosis is based on what happened, the appearance and progress of the wound, symptoms elsewhere in the body, and whether a spider can be reliably identified.

A clear photograph taken from a safe distance may help. Do not handle a spider or try to catch it if doing so could cause another bite. A dead specimen in a sealed container may sometimes be identified, but only if it can be collected without risk.

If you have significant symptoms, testing may be used to look for complications rather than to prove that a spider caused the bite. Tests may check red blood cells, kidney function, urine, or blood clotting.

Several conditions can resemble a spider bite. These include bacterial skin infections, shingles, tick bites, inflamed hair follicles, allergic reactions, and inflammatory skin disorders. A rapidly enlarging painful lump, pus-filled sore, or recurring wound may need assessment for another cause.

For a mild bite, basic first aid is often enough:

• Move away from the spider and wash the skin with soap and water
• Apply a cool pack wrapped in cloth to reduce pain and swelling
• Rest and raise the affected limb when practical
• Remove rings or tight items before swelling increases
• Avoid scratching or squeezing the area

Do not cut the wound, try to suck out venom, apply chemicals, or use a tourniquet. These actions do not remove venom and may cause further injury.

Non-prescription pain relief may be suitable for some people when used according to the label. A healthcare professional can advise if you have other medical conditions, take regular medicines, are pregnant, or are treating a child. A tetanus booster may be offered if your vaccination is not current.

Widow bites are treated with pain control, monitoring, and treatment for muscle spasms or nausea when needed. Antivenom may be considered for severe symptoms, but its use and availability differ by country.

Suspected funnel-web bites require emergency treatment and antivenom. In Australia, a pressure-immobilisation bandage is recommended while emergency help is coming. This is a firm bandage over the limb, followed by keeping the limb still. This method should not be applied routinely to other spider bites unless a poison service or emergency professional directs you to do so.

There is no broadly available treatment that reliably reverses established skin damage from a recluse bite. Care focuses on cleaning and protecting the wound, controlling pain, and watching for complications. Antibiotics like amoxicillin or doxycycline treat a bacterial infection; they do not treat spider venom and are not routinely needed.

Dead tissue may sometimes need wound care or removal. Surgery is generally considered only after the full extent of the injury is clear. Deep wounds may require specialist care or, rarely, a skin graft.

Most spider bites heal without lasting problems. Possible complications include a secondary bacterial infection, prolonged pain, or a scar.

A deeper recluse wound may take weeks or months to close. Tissue damage can leave a depressed or discolored scar. Severe whole-body reactions can cause anemia from red blood cell breakdown, kidney injury, abnormal blood clotting, or shock, although these outcomes are uncommon.

Widow venom can cause severe pain, muscle rigidity, blood pressure changes, and breathing difficulty. Funnel-web venom can rapidly cause life-threatening nervous system and breathing problems.

A serious allergic reaction is possible after many kinds of bites or stings. Swelling of the tongue or throat, wheezing, or fainting requires emergency care.

Not every spider bite can be prevented, but you can reduce the chance of being bitten.

Shake out shoes, gloves, clothing, towels, and bedding that have been stored or left on the floor. Wear gloves and covered footwear when moving firewood, boxes, rocks, or outdoor equipment. Avoid reaching into dark gaps where you cannot see.

Reduce indoor clutter and store items in sealed containers where practical. Move firewood and building materials away from living areas. Seal gaps around doors, windows, pipes, and foundations. Use care when cleaning webs or moving a spider.

Do not handle an unknown spider, even if it appears dead. Teach children to look rather than touch. If medically important spiders are common where you live, local public health or pest-control advice can help you manage them safely.

A minor local reaction often settles over several days. Redness, tenderness, or itching may fade gradually. The wound should generally become less painful and swollen rather than continue to expand.

Symptoms from a widow bite may be intense for hours or days, but most people recover with supportive care. Tiredness, soreness, or milder muscle discomfort can last longer than the most severe symptoms.

A recluse wound may change during the first several days before it begins to heal. If deeper tissue has been damaged, healing may take weeks or months and can require repeated wound checks. The final scar may remain darker, lighter, or slightly sunken.

Spider bites do not usually become a chronic condition. Once the wound and any venom effects have resolved, they do not continue to spread through the body. A past bite does not protect you from future bites.

Attend planned follow-up if the wound is open, tissue damage is developing, or dressings need to be reviewed. Routine follow-up helps track healing and identify infection or scarring; it is different from emergency care for rapidly worsening symptoms.

Call emergency services now if you have:

• Trouble breathing, wheezing, or swelling of the face, tongue, or throat
• Fainting, severe confusion, a seizure, or difficulty staying awake
• Severe or spreading muscle cramps, chest pain, or abdominal rigidity
• Heavy sweating, drooling, repeated vomiting, or muscle twitching
• A suspected Australian funnel-web bite
• Rapid deterioration after any suspected bite

Seek urgent medical assessment for dark urine, yellow skin or eyes, unusual paleness, severe weakness, or reduced urination. These can be signs of red blood cell breakdown or kidney injury.

Prompt medical advice is also appropriate for a suspected widow or recluse bite, severe pain, an enlarging blister or open sore, fever, pus, or redness spreading away from the wound. Children, older adults, pregnant people, and those with significant health conditions may need earlier assessment.

For routine follow-up, arrange a review if the wound is not steadily improving, keeps reopening, or needs ongoing dressing care. A poison information service can provide location-specific advice about dangerous spiders and first aid.

How do I know if a spider bit me?

You often cannot know for certain unless you saw the bite happen and the spider was reliably identified. A red or painful skin sore alone does not confirm a spider bite. Skin infections and other conditions are commonly mistaken for one.

What does a brown recluse bite look like?

It may begin with mild redness and later become painful, blistered, pale, blue, or purple. Some bites develop an open wound, but many do not. Appearance alone cannot confirm a recluse bite, especially outside places where recluse spiders live.

How long does a spider bite take to heal?

A mild bite may improve over several days. A deeper wound can take weeks or months. Healing time is influenced by the amount of skin damage, infection, circulation, and general health.

Can a spider bite become infected?

Yes, bacteria can enter through broken skin, although infection is not caused by the venom itself. Increasing warmth, spreading redness, pus, fever, or worsening pain should be assessed.

Should I catch the spider?

Do not risk another bite. A clear photograph from a safe distance may be useful. Only collect a dead spider if this can be done safely without touching it directly.

Can a spider bite kill you?

Death is uncommon, particularly when serious bites receive prompt treatment. Some widow, recluse, and funnel-web bites can cause severe illness. Breathing problems, widespread muscle symptoms, collapse, or rapid deterioration require emergency care.