Candling most commonly refers to one of two things: using light to check the quality or development of an egg, or a disputed alternative health practice involving hollow candles placed in the ear canal. Egg candling is a well-established technique used in both commercial poultry operations and backyard hatching, while ear candling is a practice that lacks scientific support and carries real safety risks.
Egg Candling: Using Light to See Inside the Shell
Egg candling is the process of shining a bright light through an eggshell to reveal what’s happening inside. The name comes from the original method, which literally used a candle flame as the light source. Today, LED candlers have replaced open flames, producing a cool, focused beam that won’t overheat the egg.
Candling serves two distinct purposes depending on the setting. In commercial egg production, it’s a quality control step. Eggs travel along a conveyor belt and pass over mechanical sensors paired with computerized systems that automatically detect and remove defective eggs. Hand candling, where a worker holds an egg directly in front of a light source, is still used as a spot check to verify grading accuracy. In backyard and small-scale hatching, candling lets you monitor embryo development inside incubating eggs without cracking them open.
What You Can See When Candling Eggs
When you hold a developing egg up to a bright light in a dark room, the shell becomes translucent enough to reveal the contents. What you’re looking for depends on how far along incubation has progressed. In the first few days, a fertile egg will show a small dark spot with thin blood vessels branching outward, like a tiny spider web. An infertile egg looks clear, with only a faint shadow from the yolk floating inside.
By around day 7 to 10, a healthy embryo is visibly larger, with a well-developed network of blood vessels spreading across the inside of the shell. A “blood ring,” which looks like a reddish-brown circle inside the egg, signals that the embryo has died. This ring forms when blood moves away from the embryo after death and pools in a visible band. Eggs showing blood rings should be removed from the incubator to prevent bacterial contamination of the remaining eggs.
Later in incubation, a viable egg appears almost entirely dark as the growing chick fills the space, with a bright air cell visible at the wide end. An egg that stopped developing partway through, sometimes called a “quitter,” will look partially dark but without the signs of a living, moving embryo.
How to Candle Eggs Safely
Candling won’t harm developing eggs when done properly. Just as a brooding hen naturally leaves the nest for short periods each day, you can safely remove eggs from the incubator for the few minutes it takes to candle them. Most hobbyists candle at two or three points during incubation: around day 7, day 14, and sometimes day 18.
The process is simple. Work in a dark room, hold the egg with the wide end (where the air cell sits) against the light, and look for the signs of development described above. LED candlers are preferred because they produce a cool light that won’t warm the embryo the way an incandescent bulb or actual flame would. White and light-colored shells are easiest to see through. Dark brown or speckled shells, common in breeds like Marans, require a stronger light source and can be harder to read with confidence.
Ear Candling: A Different Practice Entirely
Ear candling is an alternative health practice where a hollow, cone-shaped candle made of fabric coated in wax is placed into the ear canal and lit at the opposite end. Proponents claim it creates a vacuum, sometimes called a “chimney effect,” that draws earwax, debris, and bacteria out of the ear. A second theory suggests that the heat softens earwax so it drains out naturally over the following days. The practice is marketed for earwax removal, sinus pain relief, tinnitus, vertigo, and other conditions.
Neither theory holds up under testing. Researchers measured pressure inside an artificial ear canal during candling using a tympanometer and found that no negative pressure (no vacuum) was created at any point. The same study tested ear candling on real ears, half with impacted wax and half without. Photographs taken before and after showed that no earwax was removed from the ears that had wax in them. Even more concerning, candle wax was deposited inside the ears that started out clean. When residue left behind during candling was chemically analyzed, it turned out to be composed of alkanes found in candle wax, not ear wax. The waxy residue that practitioners sometimes show patients as “proof” the treatment worked is simply debris from the candle itself.
Risks of Ear Candling
The FDA has issued a direct warning to consumers not to use ear candles, citing three specific risks: burns to the face and ear, perforated eardrums, and blockage of the ear canal from candle wax dripping inside. Children face an even higher risk of injury and complications. No evidence supports ear candling as an effective treatment for any condition, and the practice can cause the very problems it claims to solve, particularly wax buildup and ear canal obstruction.