Chigger bites can last up to 2 weeks.
More Info: When a chigger bites, it injects saliva with an enzyme that kills the surrounding tissue causing the skin to harden and form a stylostome. It is through this stylostome that the chigger sucks out the dead tissue to feed upon. It is the presence of the stylostome that causes the extreme itching and the long healing time.
Chigger Bite Timeline
Unlike a mosquito that is relatively easy to swat when you feel it biting, the chigger is not visible to the naked eye nor is its bite immediately perceptible. Once it injects the saliva, the stylostome will begin to form within the first three hours. This is when the itching begins to set in. The area will harden, turn red, or exhibit a blister-like growth.
If the chigger is not removed, it will continue to feed which will cause the bite area to continue to grow. If it is removed through washing or itching, the stylostome will continue to itch over the next few days. The welt can take up to two weeks to finally resolve fully.