How will a brown recluse spider bite progress?

Insidiously!: First, redness, then a small central ulcer that progresses and enlarges despite all care. Secondary infection is possible, but tissue loss is because of the toxin, not usually infection. Debridement by a skilled plastic surgeon is often needed, and the wounds are difficult to heal and will leave scarring, often severe. This is not the fault of the doctor; it's the nature of the poisonous bite.

From : Center of bite it starts like a bulls eye and becomes red inflamed and sometimes necrotic.