Scientists can tell if fish have been exposed to this blue dye by checking their blood — changes in red and white blood cells are clear warning signs.

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Evidence from Studies

Supporting (1)

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Study of Hematological Alterations and Oxidative Stress in Labeo rohita Exposed to Sub-lethal Methylene Blue

Cohort Study

Animal

The study found that even small amounts of methylene blue made fish blood look abnormal, lowered their oxygen-carrying hemoglobin, and changed their white blood cell counts—proving these blood changes can be used to tell if the fish are being harmed by the chemical.

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Source Study

Study of Hematological Alterations and Oxidative Stress in Labeo rohita Exposed to Sub-lethal Methylene Blue

Score: 9

DOI: 10.55544/jrasb.3.1.58

Similar Assertions

The blue dye causes harmful chemical reactions in fish cells that damage their blood, and the more damage there is, the lower the blood’s oxygen-carrying ability becomes.

88%

The blue dye makes the fish’s red blood cells shrink and get wrinkled, which probably stops them from carrying oxygen properly.

88%

When rohu fish are exposed to a low but toxic level of a blue dye used in fish farms, their blood loses a lot of its oxygen-carrying capacity, making them very weak.

83%

Fish exposed to this blue dye show a spike in certain white blood cells and a drop in others, which means their immune system is stressed or not working normally.

78%