What to do if there are too many spiders in the house?

The short answer: Spiders are predators, a large number indoors means there is abundant prey (small flying insects). Don’t panic; most house spiders are harmless and beneficial. To reduce spiders, you need to eliminate their food source, seal entry points, and remove webs and egg sacs. Chemical spraying is only a temporary fix if you don’t address the insect population.

1. Confirm it’s spiders

• Spiders have 8 legs, two body segments, and no wings.
• They vary in size from 2–30 mm, colours from brown to grey to black.
• They build webs (most species) or actively hunt.
• You’ll find them in corners, behind furniture, near windows, and in basements.

2. Where do they come from?

• They enter through gaps in doors, windows, and vents.
• They come in from gardens, shrubs, and outdoor vegetation.
• They are attracted to light, outdoor lights attract flying insects, which in turn attract spiders.

3. Step 1: reduce food source (the root cause)

• Control other pests: fruit flies, drain flies, ants, and flying insects, these are spider prey.
• Use yellow sticky traps to catch flying insects.
• Fix moisture issues that breed fungus gnats and drain flies.
• Without prey, spiders will leave or starve.

4. Step 2: remove webs and egg sacs

• Use a broom or vacuum to remove webs from ceiling corners, light fixtures, window frames, and behind cabinets.
• Spider egg sacs are greyish-white, round (5–10 mm), attached to corners or webs, each contains dozens to over a hundred eggs. Scrape them off while cleaning webs.
• Use the crevice tool to vacuum spiders from corners and furniture.
• Wipe windowsills and corners with a damp cloth to remove pheromone trails that attract new spiders.

5. Step 3: seal entry routes

• Repair torn window screens (mesh ≤1.2 mm).
• Install weatherstripping under doors.
• Fill wall cracks and pipe openings with expanding foam or caulk.
• Check gaps around air conditioner pipes and electrical conduits.

6. Step 4: outdoor management

• Keep vegetation (shrubs, trees) at least 30 cm away from walls.
• Remove piles of leaves, wood, and debris where spiders and their prey live.
• Replace white outdoor light bulbs with yellow or amber LED bulbs, they attract fewer insects.

7. Step 5: chemical control (last resort)

• After completing the above steps, you can spray dinotefuran-containing household insecticide along corners, baseboards, and window frames.
• The residual film kills spiders that crawl over it, it lasts 2–4 weeks.
• But remember: spiders are only a symptom; if you don’t control prey, they will return.

Common mistakes

• ❌ Killing every spider you see, they help control other pests.
• ❌ Only spraying without removing webs, new spiders will build new ones quickly.
• ❌ Ignoring outdoor lighting, it lures prey and thus spiders.

Mini FAQ

Q: Are house spiders dangerous?

A: Most are harmless, only a few species (like black widow or brown recluse) pose a risk, and they are rarely found indoors in most regions.

Q: Can I use essential oils to repel spiders?

A: Peppermint oil may deter them temporarily, but it’s not a solution for an existing population.

Q: How do I know if I have a spider infestation?

A: Multiple webs, egg sacs, and frequent sightings indicate a healthy population, address the prey.

Your spider reduction list

• Control flying insects (traps, cleaning).
• Remove all webs and egg sacs.
• Seal entry gaps.
• Manage outdoor lighting and vegetation.
• Apply residual spray only if necessary.
• Accept that occasional spiders are normal.