Assume not without an allergist. The proteins that drive egg allergy are conserved across bird species, and when researchers actually challenged hen egg allergic patients with boiled quail egg, around 42 percent reacted. For comparison, the same work found about 17 percent reacted to thoroughly stone-baked hen egg, because sustained dry heat inside a matrix changes hen egg proteins in a way that boiling a quail egg does not. So a quail egg is not a step down from hen egg for an egg allergic person. If anything it is a step up.

Sustained baking inside a wheat matrix changes the shape of several egg proteins and traps others in the crumb, so a muffin or sponge presents far less recognisable allergen than a lightly cooked egg. A large share of egg-allergic children tolerate baked egg while still reacting to soft-cooked egg, and regular baked-egg eating is often part of outgrowing the allergy. Ovomucoid is the stubborn one that survives heat, which is why some children react to both. This is an allergist-supervised challenge, never a home test.

Assume not. Ovalbumin and ovomucoid, the two proteins that drive most egg allergy, are very similar between hen and duck, and skin prick studies put cross-sensitisation to duck egg white at around two thirds of hen egg allergic children. That leaves a real minority who tolerate duck egg, and separately a small number of people who react to duck or goose egg while eating hen eggs happily, so the two are not perfectly interchangeable in either direction. Either way it is a question for a supervised challenge, not a home experiment.

No. Egg grades clean for histamine content and is not graded as a histamine liberator, so plain egg is usually fine on a low-histamine diet. If eggs upset you, look at the company they keep: the aged cheese in the omelette, the leftover cooked egg that sat in the fridge for days, or a genuine egg allergy, none of which are histamine problems with the egg itself.

Because the powder is functionally raw and a cooked egg is not. Raw egg white prompts the body to release its own histamine, and the drying process for albumen powder uses heat mild enough to leave those proteins intact so the powder keeps its whipping properties. Blend it into a cold shake and you are consuming concentrated raw egg white, roughly seven whites per scoop. The same powder baked into something fully cooked loses most of that effect.