Allyson was seven, and Rob was five, when they were taking part in the movie Pound, shoot by their father. Later, miss Downey was starring in film Up the Academy.  Her parents divorced when she was fourteen, so Allyson went to the boarding school in Vermont, and unfortunately, was somewhat neglected by her parents. She graduated on the top of her class in 1980. At the age of eighteen, she moved to Washington Heights with her boyfriend and started working as a costume designer. She was working as a model and actress, but it was rather a part-time job. At 21, Allyson moved back to Los Angeles in a hope to defeat her cocaine addiction. She was living together with her younger brother Rob at that time. 

At 23 she decided to move on with her life and married for the first time. At the same time she founded a company called Downey Management, which was supposed to help the young actors with their resumes and job searches. Unfortunately, her first husband was putting her down exhausted from bulimia, drug addiction and arguments, she closed the company. She moved back to California, found herself in the New Ages studies and even was learning at college forensic psychology. Once she had finished her studies, she was travelling all around the East coast working in this sphere with the trained professionals. She moved back to New York and started working with Multiple Choice Productions. In 2002 Producers have noticed her and offered to play in the film "Tribeca's G-Spot", which Allyson was writing, directing and starring in as well. She has also appeared in the films Funny Valentine (2002), directed by 'Joel Oppenheim' and starring Anthony Michael Hall.