Yes, you can, using the filters on the right side of the screen. In the same way as you can filter your results by adding in ingredients or categories, you can also take them out. When you add an item to the filters it defaults to 'add-in' and appears below the green search bar. Just click on the + in the green filter name and the symbol changes to -, the item changes color to gray and is now "exclude' that ingredient. For more information on how to use this feature go to Excluding certain ingredients from your recipe search.
Be aware that some allergen ingredients such as butter, milk and eggs will not be listed if only small amounts are used in the recipe. So excluding those ingredients will not necessarily exclude all recipes containing them.