Bedbugs aren't known to transmit diseases to humans — although an infestation can cause significant psychological stress and lead to insomnia. But some spiders can inflict venomous bites.
According to the Mayo Clinic, of the thousands of spider species, only a few have long enough fangs and strong enough venom to inflict a dangerous bite on a human.
In the US, venomous species include the black-widow spider and the brown-recluse spider. Venomous spiders in the UK include the cellar spider, the woodlouse spider, and the false-widow spider.
Bites from certain poisonous spiders can cause severe abdominal, back, or chest pain. You might also experience fever, chills, cramping, or excessive sweating.
In very rare cases, the skin around the bite site may die within a few hours or the bite site may develop into an open ulcer. Some people also have an allergic reaction to a spider bite that compromises their ability to breathe.
You should seek immediate medical care if you notice any of these serious symptoms.