Since kids this age have a keen sense of what's theirs, your child may see the visitors as direct threats to her possessions, her parents, and herself, says Claire Kopp, Ph.D., author of Baby Steps: A Guide to Your Child's Social, Physical, Mental, and Emotional Development in the First Two Years.
But fear not: There are ways to prevent emotional meltdowns -- and at least tone down some of the family drama.
Pique her curiosity ahead of time with fun facts about the guests, such as "Did you know they have a cat the same black-and-white color as ours?"
Warn visitors that your toddler will likely need some personal space at first -- so no cheek pinching for the first hour, say.
Hold your toddler or let her stand beside you as you welcome guests. She'll feel more secure greeting new people from a safe spot.
Be calm and reassuring. Toddlers feed off your emotions, so if you're nervous, your child will be, too.
Remember, she may not want to share you with anyone, so comfort her with lots of hugs.