On the other hand, some people find that certain foods seem to make their acne worse. If that's the case, foods that clearly worsen your acne should be avoided. But be careful about jumping to conclusions, acne has many ups and downs on its own. Yes, Urushiol, the irritant principle of poison ivy, remains active for up to several years. Never handle dead plants that look like poison ivy.
Many infections can cause hives.
Colds are a common cause in children. Warts are passed from person to person, sometimes indirectly. The time from the first contact to the time the warts have grown large enough to be seen is often several months. The risk of catching hand, foot, or flat warts from another person is small. American Academy of Dermatology, 2000.