Flight crew are seated next to emergency exits during landing, they would occupy all crew seats except for any in a crew rest area (which is reached by ladder).
It's a dead body, it won't harass you. They might get rigor mortis but decomposition won't have time to start. Passengers comfort is last priority while balancing a metal tube going 900 km/h though the stratosphere. Some compensation can be arranged when back on the ground.
Acktually – IgE(/antibodies) are bound to the surface of mast cells. Antigens/allergens bind to the IgE receptor and actives the mast cell, releasing histamines. Allergy can actually be treated with anti-IgE (monoclonal) antibodies (Omalizumab)!