Callum Forster, 17, was in intensive care in hospital and his stepdad Jamie Hadland was also taken ill in Torrevieja after the family, of Ireland Wood, enjoyed a night out in July.
Callum was heavily sedated in hospital after suffering from seizures. He was later put on life support after the suspected poisoning.
The pair had been on holiday in Villamartin with Callum’s mum Helen Forster, 36, and brother Brandon, 12.
A crowdfunding appeal was launched to help the family cover their livings costs in Spain as they faced an anxious wait at Callum’s bedside.
Mr Hadland and Callum are still poorly after returning home and tests are being carried out to find out what is wrong with them, said mum Helen.
She said: “Jamie has been having seizures since he came home. Whatever happened in Spain is going to have a long term effect on both of them.
“They are still both on medication. Callum is shaking all the time and can’t sleep properly.
“The dose of medication Callum is on is still extremely high.”
Miss Forster said the family had been left with police and hospital reports which needed translating from Spanish.
She said: “It’s not easy because the hospital reports and police reports are all in Spanish.
“I’m not happy about whatever happened out there. I want some answers. People are not listening to us. I feel let down by it all.”
The Foreign and Commonwealth Office (FCO) said it had provided the family with contact details of organisations which could help with the translation. The FCO could not provide any further update on investigations into what happened. A spokesman added: “Foreign Office staff are still assisting Callum’s family.”