Boils are typically caused by Staphylococcus aureus bacteria, although they may be caused by other bacteria or fungi present on the skin surface. In addition to affecting the hair follicle, infections that cause boils will also typically involve the surrounding skin.
After an exhaustive search of my library I find no mention anywhere of any reference to moth as an omen or symbol of any kind. I will continue to look. Found this The moth is a symbol of sensitivity and impulsiveness, in dreams it can mean impending danger, and has traditionally been associated with psychic powers and their development. And of course like butterflies, they represent transformation. Apparently they're an omen of death in some cultures too.
Omen. An omen is a phenomenon that is believed to foretell the future, often signifying the advent of change. Though the word omen is usually devoid of reference to the change's nature, hence being possibly either good or bad, the term is more often used in a foreboding sense, as with the word ominous.