Patent Blue V, also called Food Blue 5 or Sulphan Blue, is a dark bluish synthetic dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

 used as a food coloring

Food coloring

Food coloring is a substance, liquid or powder, that is added to food or drink to change its color. Food coloring is used both in commercial food production and in domestic cooking...

. As a food additive

Food additive

Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

, it has E number

E number

E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E131. It is a sodium or calcium salt of [4-(α-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide inner salt. It has the appearance of a violet powder.
It is not widely used, but can be found in Scotch egg

Scotch egg

A Scotch egg consists of a hard-boiled egg wrapped in a sausage meat mixture, coated in breadcrumbs or rolled oats, and deep-fried...

s and certain jelly sweets

Gummies

Gummi candy, gummy candy, gummies or jelly sweets are a broad, general type of gelatin-based, chewy candy.Gummi bears are the most popular and well known of the gummi candies...

. Patent Blue V is banned as a food dye in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, USA, and Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

.

In medicine, Patent Blue V is used in lymphangiography and sentinel node biopsy as a dye to color lymph vessel

Lymph vessel

In anatomy, lymph vessels are thin walled, valved structures that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessels are lined by endothelial cells, and deep to that have a thin layer of smooth muscles, and adventitia that bind...

s. Though there is lot of ambiguity of the name patent blue v and it is different than food blue 5. It is also used in dental disclosing tablets

Disclosing tablets

Disclosing tablets are chewable tablets used to make dental plaque visible.The tablets, sold over-the-counter in the United States, contain a dye that stains plaque a bright color . After brushing, one chews a tablet and rinses...

 as a stain to show dental plaque

Dental plaque

Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface...

 on teeth.

It may cause allergic reactions, with symptoms ranging from itching and nettle rash to nausea

Nausea

Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, hypotension

Hypotension

In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

, and in rare cases anaphylactic shock; it is not recommended for children.PPcn}}