Why Are People Superstitious About Double-yolked Eggs?

So what causes a hen to produce double-yolk eggs? They happen when the chicken ovulates twice in quick succession, according to Sauder's Eggs, a farm in Pennsylvania. The yolk (known as an oocyte at this point), is released into the hen's oviduct (its fallopian tube) before the previous yolk has had a chance to clear out of the way. So a single shell then forms around the two yolks.

Typically, double yolks happen in young hens with more immature reproductive systems whose timing hasn't quite been perfected. It can also be a hereditary trait in heavier hen breeds like the Buff Orpington. And sometimes double-yolkers occur because of fake light exposure.

Farmers often employ artificial light to manage egg production in chickens, enabling year-round laying. Around four to five months of age, hens begin laying eggs.

Incrementally increasing their exposure to artificial light, thereby simulating longer days, helps prevent the occurrence of double-yolk eggs. However, sudden changes in day length can lead to a higher proportion of double yolks in eggs from young hens.

But things eventually even out when farmers transition the hens from controlled indoor lighting to natural light, particularly during the longest days of the year, which optimizes double-yolk production.

Over time, ovulation patterns normalize, and hens return to laying single-yolk eggs. This controlled lighting manipulation ensures a consistent egg supply.

Double-yolk eggs, although unusual, are perfectly safe to eat. They still make amazing scrambled eggs and omelets and can be used just like single-yolk eggs in most recipes.

But because the white-to-yolk ratio is off and they don't quite count as two eggs, you might have to alter certain baking recipes if you want them to come out perfectly. However, if you're making hollandaise sauce, you're in luck.

For a long time, the double-yolked egg has been considered the black sheep, if you will, of the egg world. When eggs are being processed, they go through a step called candling, during which they're examined under a light and checked for defects.

Double-yolkers usually get pulled out at that point and are not sold along with the normal eggs. But they've been enjoying a little bump in popularity, perhaps because people are becoming a bit less averse to cholesterol. (The double yolk is an extra shot of protein, after all.)

Or maybe it goes along with the general trend of interest in products from smaller farms, which is where you can sometimes find double yolks for sale. Sauder's Eggs packages the doubles separately and sells them as "Double-Yolkers."

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.