When a subject has been bitten, stung, or fed upon, the consequent lesion may be typical at the time and in its course to resolution or may be modified by scratching, secondary infection, or idiosyncratic host response. In the case of the mosquito, the lesions may be one, few, or many, depending on the insensitivity, foolhardiness, or defenselessness of the subject assailed. The lesions in Fig. 7-5 may well have been caused by mosquitoes, bedbugs, or fleas, but instead of the usual central punctum and surrounding erythema and edema, vesiculation has developed, probably signifying more-than-average host response as a result of previous sensitization. Figure 7-6 shows a more intense vesicular reaction before scratching.