There are many different kinds of ticks that can bite.
Deer ticks are usually small, no bigger than the head of a pin.
Other ticks such as wood and dog ticks are usually much larger. Most of the time there is little risk from the bite of a tick. The usual reaction is nothing more than a raised skin bump, which gets better within a few days. Occasionally, ticks can transmit infections to humans. A bite from other ticks, such as the wood tick, the dog tick, or the black-legged deer tick may cause Rocky Mountain Spotted Fever or, in extremely rare cases, a form of paralysis.