Not really. If you’re allergic to either one, your safest best is to learn to live without them.
But keep these things in mind:
You can get healthy oils elsewhere. Those good-for-you omega-3 fatty acids found in fish also come from plant sources. Leafy green vegetables, walnuts, flaxseed oil, soy oil, and canola oil are good options, but your body converts just a small amount to DHA, the type of omega-3 in fish. Talk to your doctor about vegetarian sources of DHA like microalgae (spirulina). If you’re allergic to shellfish, ask him if it’s OK to take fish oil.
Watch out for artificial seafood. Products like imitation crab meat often contain fish or shellfish.