I would go as far as to guarantee he was doing lots of opiates.
LSD and the like weren't even manufactured at that time so that's not a possibility.
A lot of people say that it was a book written by a "pedophile"
as many of the references in the book have to do with the sexual explotation of a preteen girl.
He certainly liked little girls at a level that was more than normal. However, there is no evidence at all that he was sexually attracted to them. He did photograph them in the nude, but only with permission from their mothers, and only if the children were completely at ease with it. He made sure that after his death those pictures were destroyed or returned to the children to prevent them from getting embarrassed.
In his time making nude photographs of children wasn't uncommon; all Victorian artists did studies of child-nudes, it was a trendy subject for the time. When his child-friends grew up, they told only positive stories about their warm friendship. It is suggested that Carroll loved little girls so much because he had many sisters which he loved to entertain when he was a young boy.
Google.com Sexual references in Alice in Wonderland, you'll be surprised in the amount of connections there are. About every few sentences there is one line or another that is a direct representation of either a penis, vagina, or sexual act.
Its weird.
People that say he was on LSD are misinformed and don't know history :l
As they have said the book was written in 1865.
LSD was invented in 1938...
Carroll did not use drugs while writing the story. The larger part of the story was invented when he was on a boat trip with a friend, the real Alice and her sisters. He invented it while they rowed. The drug rumor was first spread in the 1960's by supporters of the then new LSD subculture. The rumor is believed to have originated from the psychiatrists who introduced LSD into our society.