Skin Problems
Cows & Buffaloes
Photosensitization — Sunburn on the White Patches
Updated 15 Oct 2026 • By Falah Nutrition Desk, Animal Nutrition Advisor
A cow comes in from a day on fresh pasture and within a day or two the white patches on her face, back and udder go red, swell, weep and start to peel, while the black or brown areas stay perfectly normal. That one-sided damage is the signature of photosensitization: something she ate made her skin react to sunlight.
Common Signs
- Redness, swelling and later crusting only on white or pink skin — muzzle, eyelids, udder, teats, back
- Dark-skinned areas untouched
- Animal rubbing, restless, seeking shade
- Skin peeling off in sheets in bad cases
- Sometimes yellowing of the eyes and gums if the liver is involved
- Milk drop and sore teats making milking difficult
Possible Causes
- Certain plants and weeds in lush pasture (St John's wort type weeds, some clovers, buckwheat) containing light-reactive substances
- Liver damage from other plant toxins or mouldy feed, which stops the liver clearing a normal plant pigment
- Sudden move onto rich, weedy spring or autumn grazing
- Bright sun on white-faced animals
What the Farmer Should Check
- Does the damage stop exactly at the edge of the white patches?
- What new pasture, weed or fodder was eaten in the last few days?
- Are the gums or whites of the eyes yellow (liver involvement)?
- Is mouldy fodder or grain being fed?
- Can the animal be kept in shade all day for the next week?
Feed Guidance
Take the animal off the suspect pasture or fodder at once and keep her in deep shade by day. On the feed side, replace the grazing with clean dry fodder and a measured compound feed such as GOKA Star or GOKA Green so she does not lose condition while confined, and check every bag and bale for mould, since a damaged liver is often part of the picture. Plenty of clean water helps the body clear the toxin. Sore teats need gentle milking with a vet-approved soothing cream after each session. Once healed, introduce new grazing gradually and inspect it for weeds first.
Relevant GOKA Products
Dairy Cows & Buffaloes
Under 15 liters/day
Best when green fodder is scarce
Dairy Cows & Buffaloes
10-15 liters/day
Maintains milk fat, prevents repeat breeding
When to Contact a Veterinary Doctor
Severe peeling, swollen eyelids or any yellowing of eyes and gums needs a veterinary doctor: liver damage and secondary skin infection need treatment, and the vet can confirm whether a plant or mouldy feed is the source.
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