Brief Communication | Published:

Pigment chemistry

The red sweat of the hippopotamus

The red and orange pigments in this secretion account for its protective properties.


Cool customer: hippos create their own antibiotic sunscreen. Credit: P. JOHNSON/CORBIS

Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. Here we isolate and characterize the pigments responsible for this colour reaction. The unstable red and orange pigments turn out to be non-benzenoid aromatic compounds that are unexpectedly acidic and have antibiotic as well as sunscreen activity.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Eltringham, S. K. The Hippos 8–38 (Poyser Natural History Series, London, 1999).

Download references

Author information

Competing interests

The authors declare no competing financial interests.

Correspondence to Kimiko Hashimoto.

Supplementary information

Supplementary Methods (DOC 49 kb)

Supplementary Figure 1

UV-VIS spectrum of hipposudoric acid (JPG 23 kb)

Supplementary Figure 2

UV-VIS spectrum of norhipposudoric acid (JPG 24 kb)

Rights and permissions

Reprints and Permissions

About this article

Further reading

Figure 1: Structures of the red and orange pigments isolated from hippopotamus sweat.


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.