What is the phenomenon of foamy objects secreted by furniture on rainy days?

This depends on what part it is, if it is a seam, or some 3-in-1 eye opening, tenon, it may be that the wood chips inside are not cleaned when the carpenter is done, and the moisture absorbs the moisture when it rains, and it expands and comes out of the gap or the eye.

If it is the inside of the furniture, or the outside (the external possibility is relatively small because the surface is painted) foam-like objects emerge from a certain round eye, it may be that there are moths, moths and ants, and the weather will change to block the hole to prevent water and moisture, and generally pine, Tsubaki wood and other materials are more likely to be moth-eaten.

There is also the possibility that the furniture is MDF, particleboard or another way of saying that: particle board is veneered, and once a part of the skin is loose, it will swell up and squeeze out of this loose part as soon as it gets wet.

If the foam-like object is inside some cabinets, there is no paint, and the wood used may be soft or rotten and deteriorated, and the foam-like object will be dropped when it expands with moisture.

If it is a seam, or some 3-in-1 eye openings, tenons, it may be that the wood chips inside are not cleaned when the carpenter is done, and the moisture absorbs moisture when it rains, and it will come out of the gap or the opening eye as soon as it expands. If it is the inside of the furniture, or the outside (the external possibility is relatively small because the surface is painted) foam-like objects emerge from a certain round eye, it may be that there are moths, moths and ants, and the weather will change to block the hole to prevent water and moisture, and generally pine, Tsubaki wood and other materials are more likely to be moth-eaten. There is one more possibility:

Furniture is MDF, particleboard or another way of speaking: particle board veneer, once a part of the skin is loose, it expands up and squeezes out of the loose part as soon as it is wet. If the foam-like object is inside some cabinets, there is no paint, and the wood used may be soft or rotten and deteriorated, and the foam-like object will be dropped when it expands with moisture.