have failed phase II/III clinical trials, or the studies were ceased due to their unfavorable pharmacokinetics or prohibitive cost. Sphingolipids, present in yeast like Saccharomyces cerevisiae and plants, have also shown mitigative effects in animal models of gene knockout mice. Epidemiology Allergic conjunctivitis occurs more frequently among those with allergic conditions, with the symptoms having a seasonal correlation. Allergic conjunctivitis is a frequent condition as it is estimated to affect 20 percent of the population on an annual basis and approximately one-half of these people have a personal or family history of atopy. Giant papillary conjunctivitis accounts for 0.5–1.0% of eye disease in most countries. References External links Disorders of conjunctiva Allergology de:Konjunktivitis#Conjunktivitis allergica