In medicine, a<unk>  is an adverse<unk>  reaction of the skin. Most<unk> -induced cutaneous reactions are mild and disappear when the offending<unk>  is withdrawn. These are called "simple"<unk> s. However, more serious<unk> s may be associated with organ injury such as liver or kidney damage and are categorized as "complex".<unk> s can also cause hair and nail changes, affect the mucous membranes, or cause itching without outward skin changes. The use of synthetic pharmaceuticals and biopharmaceuticals in medicine has revolutionized human health, allowing us to live longer lives. Consequently, the average human adult is exposed to many<unk> s over longer treatment periods throughout a lifetime. This unprecedented rise in pharmaceutical use has led to an increasing number of observed adverse<unk>  reactions. There are two broad categories of adverse<unk>  reactions. Type A reactions are known side effects of a<unk>  that are largely predictable and are called, pharmatoxicologic. Whereas Type B or hypersensitivity reactions, are often immune-mediated and reproducible with repeated exposure to normal dosages of a given<unk> . Unlike type A reactions, the mechanism of type B or hypersensitivity<unk>  reactions is not fully elucidated. However, there is a complex interplay between a patient's inherited genetics, the pharmacotoxicology of the<unk>  and the immune response that ultimately give rise to the manifestation of a<unk> . Because the manifestation of a<unk>  is complex and highly individual, there are many subfields in medicine that are studying this phenomenon. For example, the field of pharmacogenomics aims to prevent the occurrence of severe adverse<unk>  reactions by analyzing a person's inherited genetic risk. As such, there are clinical examples of inherited genetic alleles that are known to predict<unk>  hypersensitivities and for which diagnostic testing is available.
Drug eruption
Lichenoid eruption
Streptococcal intertrigo
Polymorphous light eruption
Contact dermatitis
Acneiform eruption
Phototoxic tar dermatitis
Autosensitization dermatitis