I don't think it's serious enough to go to the doctor. I think I've even had a bite like this before. Just curious.

I react funny to mosquito and flea bites too. But this one is looking swollen. Not really discolored. I saw the bugs last night biting me. They looked like mosquitos on my knee and ankle so I brushed them off. My knee hasn't swollen really but the one on my ankle if I mash the skin around it is golf ball sized. There's no weird "head" or any bruising.

It doesn't really itch either but I can feel it. The one on my knee is more itchy.

Go to the drug store and ask the pharmacist what he would recommend you put on the spider bite. Obviously if it gets worse see a doctor.

Use meat tenderizer and water to reduce the swelling.