Cat Spider Bite: Symptoms, Treatment and When to See a Vet

Last Updated on October 8, 2026 by admin

Most spider bites on cats cause little more than a small sore, but two groups are dangerous: widow spiders (black widow, redback) and recluse spiders (brown recluse). Cats are highly susceptible to black widow venom, which causes severe pain, cramping, tremors and vomiting. Recluse bites cause a slowly spreading skin wound. If you suspect either, call your vet or an emergency clinic now.

Which spiders are dangerous to cats?

Almost all spiders have venom, but very few have fangs big enough to pierce skin and enough venom to make a mammal ill. According to the Merck Veterinary Manual, the spiders that matter for pets fall into a handful of groups, and which ones you need to worry about depends on where you live.

Cat spider bite symptoms

You will rarely see the bite happen. Merck notes that medically important US spiders don’t give a painful bite, so owners usually only suspect one once signs appear, by which time the spider is gone. What you notice depends on the type of spider.

Black widow bite signs

Merck describes cats as highly vulnerable to black widow venom, and says the outcome is often fatal. The bite itself is painful but leaves little visible damage. Signs include:

• Severe pain, crying or agitation
• Muscle cramps that start near the bite and spread
• Muscle twitching and tremors
• A hard, rigid belly
• Vomiting, diarrhea or drooling
• Wobbly walking, weakness or partial paralysis
• Breathing difficulty

Signs can begin within minutes and may come and go over a couple of days. Pet Poison Helpline lists the same pattern of muscle pain, cramping, tremors, paralysis, drooling and vomiting in cats. Only the larger female black widow, the shiny black spider with the red or orange hourglass underneath, is considered a danger.

Brown recluse bite signs

Recluse bites are painless, so the first thing you notice is usually the wound. Merck describes the typical progression:

• A small red, itchy patch
• A blister within 2–8 hours that turns into a “bull’s-eye” sore
• A pale, bluish or dark center that slowly dies off and blackens
• An open ulcer that keeps spreading and heals very slowly

Whole-body illness is rare in pets but can be life-threatening. Watch for fever, vomiting, weakness, pale gums or dark red-brown urine. These can take several days to show up.

Bites on the lip, mouth, paw or ear

Cats hunt spiders with their paws and face, so swelling on the lip, chin, nose or a paw is a common reason owners suspect a bite. A bite inside the mouth can make your cat drool, paw at its face or refuse food. Swelling around the mouth or throat that affects breathing is an emergency.

Spider bite or abscess?

A lot of “spider bites” in cats turn out to be something else. One of the most common causes of a sudden, painful lump is an abscess from another animal’s bite. VCA Animal Hospitals describes an abscess as a painful swelling that may feel firm or squishy, often with fever, and it may burst and drain foul-smelling pus. Insect stings, allergic reactions and injuries can also look like spider bites. A vet can usually tell the difference. Our guides to whether a cat abscess can heal on its own and cat bite and scratch wounds cover what to look for.

What to do if a spider bit your cat

1. Get your cat away from the spider without getting bitten yourself. Put your cat in a quiet room or a carrier.
2. Identify the spider if you safely can. A photo, or the dead spider in a sealed jar, helps your vet. Don’t waste time searching if your cat is unwell.
3. Call your vet or an emergency clinic. Tell them where you live, what the spider looked like, when it happened and what signs you are seeing. You can also call Pet Poison Helpline at (855) 764-7661 or ASPCA Animal Poison Control at (888) 426-4435 (both charge a fee).
4. Keep your cat calm and still on the way to the clinic.

What not to do

Home treatment can do more harm than good, and cats react badly to many human medicines. Unless your vet tells you otherwise, don’t:

• Give any human pain reliever. Several common ones are toxic to cats.
• Apply peroxide, antiseptics, creams or essential oils
• Cut, squeeze or try to drain the bite
• Bandage the area tightly
• Try to make your cat vomit

Cat spider bite treatment at the vet

There’s no home antidote. Treatment is mostly supportive and depends on the type of spider:

• Widow bites: Merck says the main treatment is pain and muscle-cramp control, sometimes for several days. Antivenom can speed recovery in some patients and is decided case by case.
• Recluse bites: Wound care is the core of treatment, plus antibiotics if infection sets in and pain relief. Merck notes that no recluse antivenom is available in the US, and that surgically cutting away the wound early often makes it worse. Cats with whole-body signs may need to be hospitalized with fluids and blood work.
• Tarantula hairs: Removing hairs from the eye and treating any allergic reaction.

Your vet will choose any medication and dose for your cat. Never use leftover or human medicine.

How long does a cat spider bite take to heal?

A minor bite from a harmless spider usually settles within a few days. Widow spider signs can come and go for a couple of days before they clear. Recluse wounds are the slowest: Merck notes that complete healing can take weeks to months. If a sore is still growing, darkening or draining, take your cat back to the vet.

When to call your vet

Go to emergency care now if your cat has:

• Tremors, cramps, a rigid belly, wobbliness or paralysis
• Severe pain or agitation
• Breathing trouble or swelling around the mouth or throat
• Vomiting, collapse or extreme lethargy
• A known or likely black widow or redback bite
• Dark urine, pale gums or fever after a suspected recluse bite
• Tarantula hairs in an eye, or squinting and pawing at the eye

Call your vet the same day for a sore that blisters, darkens or spreads, even if your cat seems well otherwise. If your cat stops breathing or collapses, see our guide to CPR for cats while someone calls the clinic.

Preventing spider bites

• Keep cats out of garages, sheds, woodpiles and crawl spaces, where widows and recluses hide.
• Shake out blankets, boxes and stored clothes before your cat lies in them. Recluse bites often happen when a spider gets pressed against the body.
• Cut down on clutter and seal gaps where spiders get in.
• Ask your vet before using insecticides or sticky traps anywhere your cat goes.

FAQ

Can a cat survive a black widow bite?

Yes, especially with fast veterinary care, but it’s serious. Merck describes cats as highly vulnerable and says the outcome is often fatal. Don’t wait to see whether signs get better on their own.

What does a spider bite look like on a cat?

Usually a red, swollen or tender spot. A recluse bite can turn into a blister with a pale or dark center that ulcerates over a few days. A widow bite may show almost nothing on the skin even when your cat is very sick.

Is a cat bitten by a wolf spider or house spider in danger?

Usually not. These spiders aren’t on the list of medically important species. Expect at most mild local irritation, but call your vet if the swelling grows, your cat seems unwell, or you aren’t sure what bit it.

Can a spider bite on a cat cause an abscess?

Any break in the skin can get infected, and recluse wounds can pick up secondary infections. But a sudden lump with fever is more often an abscess from a fight with another animal. Your vet can check which it is.

Should I worry about spiders in the UK?

Merck lists the European black widow and the Mediterranean recluse as the medically important species in Europe. Serious bites are uncommon, but the same advice applies: if your cat shows pain, cramping, vomiting or a spreading wound, call your vet.