What's the reaction when bleaching hair with lemon juice (citric acid)?

Is the acid working as an oxidizer or reducer with the melanin of the hair breaking down the bonds?





> 
> Hair is mainly keratin, the same protein found in skin and
>  fingernails. The natural color of hair depends on the ratio and
>  quantities of two other proteins, **eumelanin**, and **phaeomelanin**.
>  Eumelanin is responsible for brown to black hair shades while
>  phaeomelanin is responsible for golden blond, ginger, and red colors.
>  The absence of either type of **melanin** produces white/gray hair.
> 
> 
> 


[![enter image description here](https://i.stack.imgur.com/xTNKC.gif)](https://i.stack.imgur.com/xTNKC.gif)


I think the citric acid (in lemon) acts as a bleaching agent. The "bleach" reacts with the melanin in hair, removing the colour in an irreversible chemical reaction. The bleach **oxidises** the melanin molecule. 


The illustration of the molecules perhaps might give a better picture on which groups are oxidised in the process.


The melanin is still present, but the oxidised molecule is colourless. However, bleached hair tends to have a pale yellow tint. It behaves as an **oxidising agent** at least according to my findings.


Acknowledgements


1. <https://www.thoughtco.com/salon-hair-color-chemistry-602183>
2. <http://www.keratin.com/as/as002.shtml>


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