1 Poison ivy, poison oak, and poison sumac are plants than can cause an itchy rash upon contact. 2  A substance called urushiol, found in these plants, causes the rash. 3  The rash is not contagious.  The rash usually disappears in one to three weeks.
Common factors that can cause clogged ears are wax buildup, air flow blockage to the Eustachian tubes, pressure differences in the middle ear, and cold and sinus problems. Clogged ears can affect people of all ages, but is most common among children, especially when they have colds.
Plugged ears can be caused by rapid changes in ambient pressure. This is, again, a result of the auditory tube. Along with the eardrum, the auditory tube helps to equalize the pressure between the middle ear and the outer ear. This is why your ears can feel plugged when you are driving up a steep mountain or taking off in an airplane.