This chapter contains sections titled:

• Introduction

• Mast cell development

• Mast cell heterogeneity

• General morphology and biology

• Mechanisms of mast cell activation

• Role of mast cells in health

• Role of mast cells in allergic diseases

• Mast cells in asthma

• Mast cells in allergic rhinitis

• Mast cells in allergic conjunctivitis

• Mast cells in anaphylaxis

• Mast cells in atopic dermatitis (eczema) and urticaria

• Concluding remarks

• References