Moths are a diverse group of insects found globally. While generally perceived as harmless, their presence in human environments often raises questions about their potential impact. Certain aspects of their life cycle can present concerns, making it important to understand how moths might pose a danger.
Direct Health Risks
Most adult moths are harmless to humans; they do not typically bite or sting, nor do they carry diseases that commonly affect people. However, direct contact with certain moth species, predominantly during their larval (caterpillar) stage, can lead to adverse health reactions. These reactions are primarily caused by irritating hairs or scales, known as urticating hairs, that detach from their bodies.
Contact with these barbed hairs can cause skin rashes, often described as dermatitis, characterized by itching, redness, and a stinging or burning sensation. In some instances, the rash may resemble poison ivy. If these irritating hairs become airborne and are inhaled, they can trigger respiratory issues, such as sneezing, coughing, and in rare cases, asthma-like symptoms or even more severe allergic reactions.
Notable examples of caterpillars with urticating hairs include those of the tussock moth and gypsy moth. The hairs from these species can embed in the skin upon contact, leading to localized irritation. While extremely rare, some moth caterpillars, such as those from the Lonomia genus in South America, possess venom in their spines that can cause severe, even fatal, internal bleeding. Other rare venomous caterpillars, like the puss caterpillar (southern flannel moth larva), are found in the United States and can deliver painful stings.
Property Damage and Other Concerns
The primary danger moths pose to property comes from their larvae, not the adult moths. Adult moths typically have short lifespans focused on reproduction and often lack functional mouthparts for feeding. However, once eggs hatch, the resulting caterpillars can cause significant damage.
Two main categories of pest moths are responsible for property damage: fabric/clothes moths and pantry/food moths. Clothes moth larvae, such as the webbing clothes moth and casemaking clothes moth, feed on natural fibers containing keratin, a protein found in animal-based materials. They target items like wool clothing, silk, fur, cashmere, carpets, and upholstered furniture, creating holes and thinning patches in fabrics. Infestations can stem from a single item and spread throughout a home.
Pantry moths, including the common Indianmeal moth, infest and contaminate stored dry food products. Their larvae feed on items like grains, cereals, nuts, dried fruits, flour, and pet food. As they feed, these larvae spin silken webs, leave behind fecal pellets, and shed skins, rendering food unappetizing and unsafe. Beyond direct damage, adult moths can be a nuisance, often attracted to indoor lights and flying into living spaces.