Animals across various species, from household pets like dogs and cats to wild rodents, horses, and primates, instinctively lick their wounds. This ingrained action is a complex biological phenomenon. The scientific reasons behind this natural instinct reveal both immediate benefits and potential drawbacks for the animal’s recovery.
The Immediate Actions and Their Benefits
When an animal sustains an injury, the immediate physical act of licking serves several purposes. Licking helps to clean the wound by removing dirt, debris, and foreign particles, which could otherwise hinder healing or cause infection.
Beyond cleaning, licking can stimulate blood flow to the affected region. Increased circulation brings vital immune cells and nutrients to the wound site, accelerating the natural healing cascade. The physical stimulation of the wound through licking can also provide a soothing effect, alleviating some of the pain and discomfort an animal might experience. This self-soothing is a natural inclination.
The Healing Power of Saliva
Animal saliva contains various biological and chemical compounds that contribute to wound healing. Many of these components possess antimicrobial properties, helping to combat bacteria. For instance, saliva often contains lysozyme, an enzyme that attacks the cell walls of certain bacteria, and lactoferrin, which has both antibacterial and antiviral effects.
Other beneficial substances found in saliva include defensins, cystatins, and antibodies like IgA. Dog saliva, for example, has been shown to be effective against specific bacteria such as Escherichia coli and Streptococcus canis. Histatins, a type of protein, also contribute to the antimicrobial defense by targeting certain bacteria and fungi.
Beyond fighting infection, saliva also provides growth factors that promote tissue regeneration. Epidermal Growth Factor (EGF) and Nerve Growth Factor (NGF) can accelerate the proliferation of epithelial cells and nerve fibers, respectively. Saliva also contains tissue factor, which aids in blood clotting, and protease inhibitors, which protect new tissue by inhibiting enzymes that break down proteins.
When Licking Can Be Harmful
While animal saliva possesses beneficial properties, excessive or inappropriate wound licking can introduce significant risks. The mouth, despite containing helpful compounds, is also home to various bacteria. These bacteria, such as Capnocytophaga canimorsus and Pasteurella multocida, can be transferred to an open wound, leading to serious infections.
Constant licking can also irritate the wound, disrupting the process of new tissue formation and delaying healing. In severe cases, this persistent self-trauma can cause the wound to reopen or lead to a condition known as a lick granuloma, where the skin becomes raw, inflamed, and thickened. Such lesions are susceptible to secondary infections. For serious injuries, veterinary intervention and modern medical treatments are more effective and safer than relying solely on an animal’s natural instinct.