A former nursing student murdered her parents before killing herself on Father's Day, according to Hong Kong police, who suggested her skin condition may have motivated the attack.

An initial police report found that the 23-year-old had attacked her parents, inflicting fatal wounds to her father's chest, and her mother's chest, waist and legs.

Their bodies were found by police after a relative called authorities, telling them that no one had answered the door at the apartment in Tuen Mun, a residential neighbourhood of Hong Kong.

A 30-centimetre knife, which was suspected to have been used in the attack, was recovered at the scene, police said.

The couple's daughter Pang Ching-yu was also found dead at the scene. Police said they found a suicide note in Pang's bedroom saying she was bothered by long-term eczema.

Eczema is a chronic skin condition which is characterized by dry, itchy skin, which can also blister, ooze fluid, scale and thicken. It can have a hereditary component but is exacerbated by environmental factors including the weather, pollution and stress.

The woman had also posted in an online forum blaming her parents for the condition.

"People with eczema giving birth to kids are worse than poor people giving birth to kids," the post reads. "If you're poor, you can rely on your own hard work. With eczema, sorry, you have to suffer (your whole life) with no change."

Pang had earlier written in the forum that she suffered side effects from steroids that she was using to treat the condition, which made her skin uncomfortable. She added that having the condition meant "there's nothing you can do except to wait and die," and that her "social life (was) all gone."

The skin condition affects around 30% of the US population -- most of whom are children and adolescents, according to the National Institute of Allergies and Infectious Diseases (NIAID).

Children whose parents have the condition, or asthma and allergies are "more likely to develop atopic dermatitis (eczema) than children of parents without allergic diseases," the NIAID says.

The police investigation into the deaths is ongoing. (CNN)

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