Hi, Almost all insect bites or stings leave welts, if they have the horsepower to break the skin.It s their saliva can also cause a localised allergic reaction. Red welts, initially appear as mosquito bites, farmore itchy, from blister and liquid and turns yellowish. A welt showing up suddenly may very well be a bite - possibly even from a spider.But figuring out what caused the bites is nearly impossible without catching the culprit in the act. Most spider bites can t be confirmed as being caused by spiders or as being bites at all. Almost all spiders are venomous. Most spiders are too small, or their venom too weak, to be dangerous to humans. Local reaction to bites from all kinds of toxic bugs look the same redness, swelling, itching etc. Neem powder + Turmeric powder, make paste with honey. Apply as an anti- itch cream. Apply Aloe vera gel as a anti - inflammatory.