The present invention relates to compounds of formula (I) for use as pharmaceutical active compounds, as well as pharmaceutical formulations containing the same, for the treatment of allergic diseases. The compounds according to Formula (I) are suitable as modulators of CRTH2. The invention provides Spiro derivatives according to Formula (I) and related formulae that are useful in the treatment and/or prevention of diseases selected from allergic diseases such as allergic asthma, allergic rhinitis, allergic conjunctivitis, and inflammatory dermatoses such as atopic dermatitis, contact hypersensitivity, allergic contact dermatitis, chronic urticaria/chronic idiopathic/autoimmune urticaria, drag-induced exanthems (e.g., toxic epidermal necrolysis or Lyell's syndrome/Stevens-Johnson syndrome/drug hypersensitivity syndrome), photodermatosis or polymorphous light emption (e.g., photoirritant contact dermatitis, photoallergy contact dermatitis, chronic actinic dermatitis), and myositis neurodegenerative disorders such as neuropatic pain and other diseases with an inflammatory component such as rheumatoid arthritis, multiple sclerosis, osteoarthritis, and inflammatory bowel disease (IBD).