Is it unhealthy to lick the lid of a yogurt cup?

Question

I've heard that it's unhealthy to eat the yogurt that sticks to the lid because it contains aluminium. Scraping it off with a spoon is even worse than licking it.

Is there any evidence that this is true? What about food that sticks to aluminium foil?

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Apparently, this is not a common issue in the English-speaking world. Googling for "yogurt lid unhealthy" reveals this question as the 7th entry and, except for one poll, all other hits are about yogurt in general. In Germany, this issue is apparently much hotter. Here is Stern (news magazine), n-tv (news channel), Abendblatt (newspaper), and a health portal discussing the problem. They all conclude that it's not true, but don't provide sources for their claims.

I'll quote from these articles to show the relevance of the claim.

(stern.de)
Daneben bewegt viele Menschen aber die Sorge, ob beim Ablecken Aluminium aufgenommen wird[...]
Many people are moved by the fear that aluminium is absorbed through licking

(haushaltstipps.net)
Aluminium steht im Verdacht, an der Entstehung von Alzheimer beteiligt zu sein, und Joghurtdeckel bestehen aus diesem Metall. So hört man viele Eltern ihre Kinder ermahnen, dass sie die Joghurtdeckel auf keinen Fall ablecken sollen.
Aluminium is suspected to play a role in the development of Alzheimer's and yogurt lids are made of this metal. Thus, many parents warn their children to never lick the lids.

(fid-gesundheitswissen.de
Diese Frage wird immer wieder gestellt, es kursieren sogar Gerüchte, dass der Deckel nicht nur Alu abgeben würde. Häufig wird davor gewarnt, solche Alu-Deckel abzulecken, weil er Antibiotika, Konservierungsstoffe oder aber lösliches Gift enthalte.
This question is asked again and again, there are even rumors that the lid dispenses not only aluminium. Often it is warned not to lick the lids because they contain antibiotics, preservatives or soluble poisons.

Answer 1

According to a statement/paper from the CDC (American government), the effects oral exposure to small amounts of aluminum causes no significant harm. Large amounts are linked to Alzheimer's and kidney stones in some studies (others dispute this), but this is mostly in reference to waste dumps.

Also in the same paper "You cannot avoid exposure to aluminum because it is so common and widespread in the environment." in reference to eating aluminum in foods. In conclusion, exposure to aluminum is inevitable, and while the process of licking a lid will cause you to ingest some, it will not be enough to be hazardous. Unless you are eating the lids whole, and several a day, you should be fine.

Source: How can aluminum affect my health?