The Common House Gecko (Hemidactylus frenatus) is a South-East Asian lizard.
In some parts of India, there are various beliefs about the them, or their urine, being toxic to eat. Wikipedia describes them as superstitions:
Geckos are considered poisonous in many parts of the world.
On the other hand, this 2011 newspaper article attributes the deaths of two children to a lizard falling in milk:
According to residents, Shabli Baloolwala resident Ishrat Bibi was boiling milk for her two sons Umar, 7, and Najeeb, 4, but forgot to cover the lid of the kettle. While, she was working in the kitchen a lizard fell into the kettle.
After boiling the milk, Ishrat Bibi placed it in the freezer and served it to her kids at noon. Both boys immediately began vomiting and collapsed. Ishrat and her husband Fateh Khan rushed the boys to the hospital but both boys died before they could be provided any medical aid.
Meanwhile, this Open Access Journal article abstract declares that to be impossible:
The reason behind the food-poisoning due to felling of house geckos in eatables is described in this paper. House geckos are known to carry various types of pathogens in their bodies which cause food-poisoning after consuming the contaminated foods. Since these geckos are non-poisonous, the food poisoning due to their presence in food is not possible.
Are Common House Geckos poisonous?