eli5; Why do people have unique smells?

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Everybody has unique smell, not like perfume or any cosmetic but something else. and it doesnt smell bad it just smells different. im wondering if its related to genetics or diet or something else or a combination of things.

In: Biology

Mammals such as mice and humans are known to have unique, genetically determined body odors, called odortypes, which act something like olfactory nametags, helping distinguish to individuals from one another, even pick out a mate.

An individual’s odortype is determined in part by genes in a genomic region called the major histocompatibility complex (MHC), which plays a role in the immune system and are found in most vertebrates.
The type of food an animal or person eats can influence their body odor; garlic, when consumed in large amounts, is a well-known example. Researchers at the Monell Chemical Senses Center in Philadelphia looked into the question of whether or not changes in diet could possibly get in the way of one’s genetically determined odortype and thus mask aromatic identity. Genetically determined odortypes persisted regardless of what the mice ate, even though dietary changes did strongly influence the odor profiles of individual mice. Both the sensor mice and chemical analyses could still detect the underlying odortypes. [source](https://www.livescience.com/5188-odor-unique-fingerprint.html)