Eosinophilic pneumonia, also known as eosinophilic pneumonitis is a rare disease where a type of white blood cell called an eosinophil accumulates in the lungs. The eosinophils accumulate in the air sacs of the lung, interfering with the transfer of oxygen. It can be acute, in which case the disease develops very quickly, or chronic, in which case its progression is far slower. In less developed countries, it is almost always set off by some type of parasitic infection. However, it can be set off in some patients by certain medications including such common ones as ibuprofen and ampicillin. It can also be caused by abuse of heroin or cocaine. However, many cases are ideopathic.