Minoxidil is typically of a transparent color. But sometimes, it can also be a yellowish color.
This begs the following questions, why is my minoxidil yellow? And is it a bad thing if my minoxidil turned yellow?
Let me explain why minoxidil can be, or turn yellow over time.
Why is my minoxidil yellow colored?
So why is minoxidil yellow? Well, mainly because of two reasons.
Retinol
Some brands of minoxidil have retinol as an ingredient. Retinol has a yellow color, which consequently explains why your minoxidil can have a yellowish color.
But don’t worry, the yellow color will not be noticeable once it’s applied to the scalp.[1]https://www.minoxidillaboratory.com/minoxidil-frequently-asked-questions/
Sometimes, the yellow minoxidil color can slowly develop when the minoxidil solution ages. This is due to the retinol and possibly azelaic acid aging. This is especially observable if the solution is poured in a transparent glass or natural color plastic bottle.[2]https://www.minoxidilmax.com/should-15-minoxidil-5-azelaic-acid-formula-be-yellowish
Oxidation
It’s also possible that your minoxidil turned yellow due to oxidation.
The drops of minoxidil solution or foam that have fallen around the cap or outside the bottle can also turn yellow. This is because the minoxidil has come into contact with oxygen, which triggers the process known as oxidation.
Consequently, if you’ve left your minoxidil bottle open, the minoxidil inside can turn yellow over time as well due to oxidation.
Final note
Minoxidil can be/turn yellow due to having retinol as an ingredient, or because of oxidation when the product came into contact with oxygen.
Nevertheless, yellow minoxidil typically shouldn’t be problematic since it does not diminish the efficiency of minoxidil foam or solution.