( ( ( The cause ) ( of ( these ( painful ( fluid-filled bumps ) ) ) ) ) ( ( ( ( includes ( ( the friction ) ( of ( ill-fitting ( or ( stiff shoes ) ) ) ) ) ) and ) ( ( wrinkled socks ) ( against ( the skin ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN cause)) (PP (IN of) (NP (DT these) (JJ painful) (JJ fluid-filled) (NNS bumps)))) (VP (VP (VBZ includes) (NP (NP (DT the) (NN friction)) (PP (IN of) (NP (JJ ill-fitting) (CC or) (JJ stiff) (NNS shoes))))) (CC and) (VP (VBD wrinkled) (NP (NNS socks)) (PP (IN against) (NP (DT the) (NN skin))))) (. .)))
The cause of these painful fluid-filled bumps includes the friction of ill-fitting or stiff shoes and wrinkled socks against the skin.
(ROOT (S (NP (NN Friction) (NN force)) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NP (JJ microscopic) (NNS bumps)) (, ,) (VP (VBZ lumps)) (, ,) (CC and) (NP (NP (NNS imperfections)) (VP (VBG colliding))))))) (. .)))