Skin testing remains an essential diagnostic tool in modern allergy practice. A signifi cant variability has been reported regarding technical procedures, interpretation of results and documentation. This review has the aim of consolidating methodological recommendations through a critical analysis on past and recent data. This will allow a better understanding on skin prick test (SPT) history; technique; (contra-) indications; interpretation of results; diagnostic pitfalls; adverse reactions; and variability factors. Skin has an important physiological role in the internal balance homeostasis and constitutes a crucial barrier against external aggressions, with well-known immunological properties. 1 It has been used by allergists for decades as an easily assessed laboratory of the immunological status of the individual.The fi rst skin testing technique was developed by Charles H. Blackley in 1865, a Manchester homeopathic physician with allergic rhinitis. He abraded a quarter-inch area of his skin with a lancet and then applied grass pollen grains. 2 The so-called scratch test was later adopted by Schloss for the diagnosis of food allergy in children. 3 Epicutaneous tests can be divided into scratch tests and prick/puncture tests. The fi rst method, proposed by Blackley 2 , implied a linear scratch without drawing blood and could either be performed fi rst, with the extract then dropped on the abraded skin, or be made through a drop of extract. 4 Although it was used extensively in the past, this technique became progressively obsolete due to patient discomfort, poor reproducibility, possible residual lesions and newer and innocuous procedures. 4 Therefore, scratch test is mentioned here for historical purposes only. It was Sir Thomas Lewis who, in 1924, fi rst applied skin prick tests (SPT). 5 Nevertheless, their generalised use in clinical practice only became a reality about 30 years ago, as a result of technique modifi cations proposed by Pepys. 6 For the purpose of this review and for easier comprehension, skin testing will be referred interchangeably as SPT, whatever device is used for its application.In 1966, Ishizaka's work on immunoglobulin E (IgE) and immediate hypersensitivity reactions 7 established the scientifi c corpus to what was done till then on a strictly empiric basis.As written by Dr Walzer in 1974, "the fact that skin testing has not turned out to be a simple and completely reliable technique does not detract from the fact that, when it is intelligently and skilfully performed, it remains the most effective diagnostic procedure in reaginic allergic disorders". 8 The reliability of skin testing and proper documentation of test results are essential in allergy practice. A recent survey to all physician members and fellows of the American College of Allergy, Asthma and Immunology practicing in the