Can you have a serval even if you are allergic to cats?

As a general rule, wild animals make very poor pets. Big cats don't have the same instincts that domestic cats do. They are notoriously hard to litter train and often really need a lot more space, sometimes including some sort of outdoor enclosure.

If you want a bigger cat that has that look and is kind of wilder, look at Savannah cats. They are descended from the servals but are better adapted to house living.

Other than that you'd have to check with your local dept of fish game and wildlife to find out rules on owning a wild cat.

Servals are very expensive and make terrible pets. Each year 30000 cats are put to sleep because they cannot find homes. Adopt a cat from your local shelter and donate money to help preserving small cats in the wild.