A MAN'S hair turned white overnight in the "first case" of a rare side effect to chemotherapy.

The 62-year-old looked decades older one morning when he woke up - after just a few weeks of treatment with no warning sign.

The patient, from Croatia, was on the chemotherapy drug pazopanib for kidney cancer.

Hair colour change is a common side effect of using the drug, but it usually happens gradually over a few months.

According to his doctors it's the "first such case reported" of hair colour changing so quickly.

The patient had begun treatment for a mass in his kidney just over a month before he went grey.

He had surgery to remove part of the mass then was put on daily doses of pazopanib.

Within the first month he begun suffering with high blood pressure as a side effect of the treatment.

Therapy was stopped for two weeks until his blood pressure could be stabilised, he was then put back on Pazopanib.

But a few days later he began complaining of abdominal pain, vomiting and nausea.

He was admitted to Klinicki Bolnicki Centar Zagreb hospital where doctors discovered his cancer had spread to his lungs.

He was later sent home and treated for two more days on pazopanib before waking up the next morning to discover his hair and eyebrows had turned "completely white during the night".

The drug continued to cause him abdominal pain and high blood pressure, so doctors discontinued the treatment for seven weeks.

But during that time his hair stayed white.

He was eventually put back on Pazopanib and at a three month follow up his tumours had begun to shrink and his hair colour was slowly restoring.

Dr Ana Tečić Vuger, who treated the man, noted in the British Medical Journal case report that some forms of chemotherapy drugs can alter chemicals in the hair follicle responsible for colour.

"Reported incidence of hair colour changes in patient treated with pazopanib is about 35 per cent according to drug-safety studies," she wrote.

"In a few reported cases, hypopigmentation was first noted after 1–5 cycles of therapy and it gradually developed to maximum after 6–10 cycles.

"In our research, we found no clinical or literature data of rapid (overnight) loss of hair pigment due to therapy.

"To the best of our knowledge, this is the first such case being reported."

In other cases of hair colour fading, patient's experience gradual colour change and were under great physical, emotional or mental stress.

None lost their hair colour overnight.