The causes of skin reaction due to parasites in dogs lie in connection with the individual habits and behaviors of each type of parasite:
Fleas
These external parasites can be found virtually anywhere where other dogs and cats go, either seasonally or year-round since they thrive in warm and humid conditions. Adult females can produce up to 50 eggs per day and they can begin doing so within 24 hours of inhabiting your doggy family member. These eggs can fall off your pet in his normal living routine to contaminate his bedding, the sofa, your bed (if he joins you there) and anywhere else he goes, whether inside or outside of the house (yes, in your car, too). They can then hatch into tiny larvae and burrow into surrounding elements, spin their cocoon and live for weeks without a warm blooded host. The life cycle of a flea can range from 12 days to 6 months and, when they emerge from their cocoon as adults, the cycle begins all over again. The resulting health issues with your pet are the skin irritations, skin infections, anemia (since they feed on the blood of the host) and intestinal tapeworms of various types.
Mites
There are various species of mites, for example ear mites, sarcoptic mange mites, and demodectic mange mites. Some are more contagious than others, but they can all cause severe skin reactions which are very unsightly, uncomfortable for your pet, and potentially dangerous to the health of your pet, as the constant irritation and scratching has the potential to create opportunity for skin infections, some of which can be very serious and difficult to treat successfully
Ticks
This is another parasite which gets on the host and buries its head into the skin of the host to feed on its blood. They’re found anywhere in wooded areas and underbrush as a general rule and aren’t really very picky about from whose blood they get their nourishment. They have the ability to spread serious infectious diseases like Lyme Disease and Rocky Mountain Spotted Fever to their hosts.