The Food and Drug Administration (FDA) is going after a San Francisco food manufacturing startup. Why? Because of its labels.

Food maker Hampton Creek started off with good intentions in making a vegan mayonnaise substitute. It created an all vegetable-based vegan mayonnaise that uses the Canadian yellow field pea. A type of split pea, as an egg substitute and key ingredient.

Hampton Creek dubbed the product “Just Mayo” and placed the branding below the image of a cracked egg. The crack being negative space in the shape of a plant. It launched late in 2013 and, by all accounts, it was a successful representation of mayonnaise. But the problem with the product wasn’t the taste, but rather its labeling.

Just a little over a year after Just Mayo hit store shelves, Hampton Creek was sued by Unilever. The parent company that owns the popular Hellmann’s brand of mayonnaise. Its argument was that Hampton Creek cannot call its product “mayo” if it has no egg.

In 1957, the FDA created a formal definition of mayonnaise as containing 65 percent vegetable. And at least one ingredient that contains an egg yolk.

So, not only does Just Mayo not have egg, but Hampton Creek put an egg right on the label.

Unilever ultimately dropped the case, but the FDA was watching closely and issued a formal. Warning to Hampton Creek last month.

“‘Just’ together with ‘Mayo’ reinforces the impression that the products are real mayonnaise by suggesting. That they are ‘all mayonnaise’ or ‘nothing but’ mayonnaise. However, your Just Mayo and Just Mayo Sriracha do not meet the. Definition of the standard for mayonnaise,” the FDA wrote in a letter.

The FDA also took exception to the company’s claims of Just Mayo being cholesterol-free. According to the FDA, in order to advertise that, foods cannot have over 13 grams. Of fat per 50 grams of product, which Just Mayo has.

The story is still ongoing, but it speaks to the delicacy of food labeling and branding. Just because something is catchy doesn’t mean it’s appropriate. With color label printers, brands can take their marketing strategy into their own hands.